JP2004360890A - Power transmission mechanism control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device capable of appropriately and accurately setting a pressure applied to a power transmission mechanism.
SOLUTION: In a control device for a power transmission mechanism in which a transmission torque capacity changes according to an applied pressure, a slip start pressure at which a slip starts when a predetermined input torque is applied and a slip start pressure based on the slip input pressure. A pressure setting means is provided for setting the pressure applied to the power transmission mechanism by a physical quantity determined from a determined theoretical pressure.
[Selection diagram] Fig. 1

Description

  The present invention relates to a control device for a power transmission mechanism, such as a continuously variable transmission or a friction engagement device, whose transmission torque capacity changes according to applied pressure.

  Belt-type continuously variable transmissions and traction-type continuously variable transmissions transmit torque by using the frictional force between a belt and a pulley and the shearing force of traction oil between a disk and a roller. A friction engagement device such as a brake transmits torque using a friction force generated on a surface of a friction material. Therefore, in these power transmission mechanisms, the transmission torque capacity is set according to the pressure acting on the point where the transmission of the torque occurs.

  The above-mentioned pressure in the continuously variable transmission is referred to as a clamping pressure, and may be referred to as an engagement pressure in a frictional engagement device. By increasing the clamping pressure or the engagement pressure, the transmission torque capacity is increased. Although slipping can be avoided by doing so, power is unnecessarily consumed to generate high pressure, or power transmission efficiency is reduced. Therefore, in general, the squeezing pressure or the engagement pressure is set as low as possible without causing unintentional slippage.

  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 squeezing pressure is controlled to be set as low as possible without causing slippage. For that purpose, it is necessary to detect the pressure at which the slip starts (that is, the slip start pressure). Conventionally, the slip is detected by various methods, and the slip start pressure is detected.

  For example, Patent Document 1 describes a method of determining a slip limit by changing a pressing force when a condition regarding a transmitted force, a speed, a transmission ratio, or a combination thereof is at least substantially constant. Have been. The invention described in Patent Document 1 is directed to a continuously variable transmission including a pair of conical discs and a winding transmission wound around the pair of conical discs, and reduces the crimping force of the pair of conical discs. , The slip between the pair of conical disks and the winding transmission is determined from an increase in friction efficiency (that is, an increase in oil temperature).

Further, in the invention described in Patent Document 1 described above, a characteristic field indicating a required pressure force for a specific slip, which is related to various rotational speeds, torques, speed ratios, and temperatures, is stored, It is stated that the pressing force between the conical disks is adjusted in accordance with this characteristic field.
JP 2001-12593 A

  In the method described in Patent Document 1 described above, slip when the pressure is reduced is detected by an increase in friction efficiency. Since a time delay inevitably occurs between the time when the ascent is detected and the time when the rise is detected, even if the crimping force is increased stepwise by the establishment of the slip determination, the slip may be excessive. In addition, since the crimping force is increased when the increase in friction efficiency is detected, if the increase in friction efficiency is not detected for some reason, the crimping force is further reduced. As a result, there is a possibility that excessive slippage may occur due to an increase in the reduction width of the pressing force.

  Furthermore, when gradually decreasing the pressing force to cause slip, if the decrease gradient is small, it takes a long time to detect slip, and in the process, the operating state changes and the detection of slip must be stopped. May be lost. Conversely, if the gradient of the decrease in the pressing force is increased, excessive slip may occur due to overshoot, which may result in damage such as abrasion.

  Further, in the method described in Patent Document 1 described above, the slip limit, that is, the slip starting pressure is determined by changing the pressing force. However, the slip starting pressure is reflected in appropriate control of the power transmission mechanism. No specific method is mentioned.

  The present invention has been made in view of the technical problem described above, and has as its object to provide a control device that can appropriately, accurately, and easily set a pressure applied to a power transmission mechanism. It is.

  In order to achieve the above object, according to the first aspect of the present invention, in a control device for a power transmission mechanism in which a transmission torque capacity changes according to an applied pressure, slippage occurs in a state where a predetermined input torque is applied. A control device comprising pressure setting means for setting the pressure applied to the power transmission mechanism by a physical quantity determined from a slip start pressure to start and a theoretical pressure determined based on the input torque.

  According to a second aspect of the present invention, there is provided the control of the power transmission mechanism according to the first aspect, further comprising learning means for learning and correcting the physical quantity based on an operation state of the power transmission mechanism. Device.

  Further, according to a third aspect of the present invention, in the second aspect of the present invention, the power transmission mechanism includes a continuously variable transmission that continuously changes a gear ratio and changes a torque capacity according to a squeezing force; The control device for a power transmission mechanism, wherein the learning means includes a means for learning the physical quantity based on at least one of an input rotation speed, an input torque, and a gear ratio for the continuously variable transmission.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, the power transmission mechanism includes a continuously variable transmission that continuously changes a gear ratio and changes a torque capacity according to a squeezing force; The control device for a power transmission mechanism, wherein the learning means includes means for learning and correcting the physical quantity based on a function of a speed ratio of the continuously variable transmission.

  According to a fifth aspect of the present invention, the learning means according to the fourth aspect of the present invention includes a means for calculating a change in a coefficient of friction in the continuously variable transmission as a function of the speed ratio and learning and correcting the physical quantity. A control device for a power transmission mechanism, characterized in that:

  Therefore, according to the first aspect of the invention, when setting the pressure to be applied to the power transmission mechanism to set the transmission torque capacity, the slip start pressure is detected by a predetermined method while a predetermined input torque is applied. The theoretical pressure is set based on the input torque. Then, the physical quantity set based on the slip start pressure and the theoretical pressure is reflected in the control, and the pressure is set. As a result, the pressure applied to the power transmission mechanism can be set appropriately.

  According to the second aspect of the present invention, the physical quantity set based on the slip start pressure and the theoretical pressure is learned and corrected in accordance with a change in the operation state of the power transmission mechanism. Therefore, for example, when the operating state of the power transmission mechanism changes from a steady state to an unsteady state, or in a transitional state, the physical quantity is appropriately corrected and the pressure applied to the power transmission mechanism is reduced. It can be set appropriately and accurately.

  Further, according to the invention of claim 3, when the power transmission mechanism includes a continuously variable transmission, the physical quantity set based on the slip start pressure and the theoretical pressure is equal to the input rotational speed of the continuously variable transmission. Learning correction is performed based on at least one of the input torque and the gear ratio. As a result, when the operating state of the power transmission mechanism changes from the steady state to the non-steady state, or when the power transmission mechanism is in the transient state, the physical quantity can be appropriately corrected by appropriately reflecting the state change.

  According to the invention of claim 4 or claim 5, when the power transmission mechanism includes a continuously variable transmission, the physical quantity set based on the slip start pressure and the theoretical pressure is controlled by the continuously variable transmission. Learning correction is performed based on the function of the gear ratio of the machine. As a result, it is possible to appropriately correct the physical quantity by reflecting a change in the power transmission state such as a friction coefficient of a power transmission unit of the power transmission mechanism, and prevent a reduction in a safety factor against slippage of the continuously variable transmission. Alternatively, it can be suppressed. Further, the learning map is simplified, and the clamping pressure control based on the limit clamping pressure can be easily executed.

  Next, the present invention will be described based on specific examples. First, an example of a transmission system including a power transmission mechanism according to the present invention will be described. FIG. 3 schematically illustrates a drive mechanism including a belt-type continuously variable transmission 1 as a power transmission mechanism. 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 having a lock-up clutch 3.

  The power source 5 includes an internal combustion engine, an internal combustion engine and an electric motor, or an electric motor. In the following description, the power source 5 is referred to as an 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 opposite to the pump impeller, and a stator disposed therebetween. It is configured to supply a spiral flow of fluid generated by a pump impeller to the turbine runner to rotate the turbine runner and transmit torque.

  In the transmission of torque through such a fluid, inevitable slippage occurs between the pump impeller and the turbine runner, which causes a reduction in power transmission efficiency. And a lock-up clutch 3 for directly connecting to an output-side member such as The lock-up clutch 3 is configured to be controlled by hydraulic pressure, is controlled to a fully engaged state, a completely released state, and a slip state that is an intermediate state between these states, and can appropriately control the slip rotation speed. It has become.

  The forward / reverse switching mechanism 2 is a mechanism that is employed in accordance with the fact that the rotation direction of the engine 5 is limited to one direction, and outputs the input torque as it is, and outputs it in reverse. 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, the ring gear 7 is arranged concentrically with the sun gear 6, and between the sun gear 6 and the ring gear 7, a pinion gear 8 meshed with the sun gear 6 and another pinion gear 9 meshed with the pinion gear 8 and the ring gear 7 are arranged. The pinion gears 8 and 9 are held by the carrier 10 so as to rotate and revolve. Further, a forward clutch 11 for integrally connecting the two rotating elements (specifically, the sun gear 6 and the carrier 10) is provided, and by selectively fixing the ring gear 7, the direction of the output torque is provided. Is provided.

  The continuously variable transmission 1 has the same configuration as a conventionally known belt-type continuously variable transmission, and each of a drive pulley 13 and a driven pulley 14 arranged in parallel with each other includes a fixed sheave and a hydraulic pulley. And a movable sheave that is moved back and forth in the axial direction by actuators 15 and 16. Therefore, the groove width of each of the pulleys 13 and 14 changes by moving the movable sheave in the axial direction, and accordingly, the winding radius of the belt 17 wound around each of the pulleys 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 the carrier 10 which is an output element of the forward / reverse switching mechanism 2.

  A hydraulic pressure (line pressure or its correction pressure) corresponding to the torque input to the continuously variable transmission 1 is supplied to the hydraulic actuator 16 of the driven pulley 14 via a hydraulic pump and a hydraulic control device (not shown). I have. Therefore, when each sheave of the driven pulley 14 sandwiches the belt 17, tension is applied to the belt 17, and a clamping pressure (contact pressure) between each pulley 13, 14 and the belt 17 is secured. . On the other hand, pressure oil corresponding to the gear ratio to be set is supplied to the hydraulic actuator 15 in the drive pulley 13 so that the groove width (effective diameter) according to the target gear ratio is set. .

  The driven pulley 14 is connected to a differential 19 via a gear pair 18, and outputs torque from the differential 19 to driving wheels 20. Therefore, in the above drive mechanism, the lock-up 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 to detect the operation state (running state) of the vehicle equipped with the above-described continuously variable transmission 1 and the engine 5. That is, a turbine speed sensor 21 that detects an input speed (speed of the turbine runner) to the continuously variable transmission 1 and outputs a signal, and an input speed that detects a 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 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 particularly shown, an accelerator opening sensor that detects the amount of depression of the accelerator pedal and outputs a signal, a throttle opening sensor that detects the opening of the throttle valve and outputs a signal, and a brake pedal are depressed. A brake sensor or the like that outputs a signal in the case is provided.

  In order to control the engagement / disengagement of the forward clutch 11 and the reverse brake 12, control the squeezing force of the belt 17, control the gear ratio, and control the lock-up clutch 3, the transmission Electronic control unit (CVT-ECU) 25 is provided. The electronic control unit 25 for a transmission is mainly configured by a microcomputer as an example, performs calculations in accordance with a predetermined program based on input data and data stored in advance, and performs various operations such as forward, reverse, and neutral. And the setting of the required squeezing pressure, the setting of the gear ratio, the engagement / disengagement of the lock-up clutch 3, and the control of the slip rotation speed and the like.

  Here, as an example of data (signal) input to the transmission electronic control unit 25, a signal of an input rotation speed (input rotation speed) Nin of the continuously variable transmission 1, an output of the continuously variable transmission 1 A signal of the number of rotations (output rotation speed) No is input from the corresponding sensor. An engine electronic control unit (E / G-ECU) 26 for controlling the engine 5 outputs a signal of an engine speed Ne, a signal of an engine (E / G) load, a throttle opening signal, an accelerator pedal (not shown). ) 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 same can be improved. For example, a target driving force is determined based on a required driving amount and a vehicle speed represented by an accelerator opening, and a target output required to obtain the target driving force is determined based on the target driving force and the vehicle speed. The engine speed for obtaining the target output at the optimum fuel efficiency is obtained based on a prepared map, and the gear ratio is controlled so as to become the engine speed.

  In order not to impair such an advantage of improving fuel efficiency, power transmission efficiency in the continuously variable transmission 1 is controlled to a favorable state. Specifically, the torque capacity of the continuously variable transmission 1, that is, the belt clamping pressure is set to a value as low as possible within a range where the target torque determined based on the engine torque can be transmitted and the belt 17 does not slip. Controlled. The control reduces the clamping pressure to cause a slight slip in the continuously variable transmission 1. The clamping pressure at that time is defined as a sliding starting pressure, and the slipping starting pressure is a hydraulic pressure or a road pressure from a predetermined safety factor. This is executed by setting the pressure to the pressure corresponding to the input.

  The control device according to the present invention is configured to perform control for lowering the squeezing pressure, detection of slip, and setting of the squeezing pressure thereafter. 1 and 2 are block diagrams for explaining an example of the control.

  Referring to FIG. 1, a case will be described in which the clamping pressure is gradually reduced, belt slip due to the clamping pressure is detected, and the slip starting pressure, that is, the limit clamping pressure is learned and corrected. First, a belt slip is caused by the control for lowering the clamping pressure, and the rotation speed of the driven pulley 14 when the slip is detected, that is, the output shaft rotation speed Ns is detected (block B1). Then, a pressure Phard corresponding to the sum of the centrifugal hydraulic pressure acting on the driven pulley 14 and the spring force of the hydraulic actuator 16 is obtained from the output shaft rotation speed Ns (block B2).

  The rotation speed of the drive pulley 13 at the time of slip detection, that is, the input shaft rotation speed Nin (that is, the engine rotation speed Ne) is detected (block B3), and the speed is changed from the input shaft rotation speed Nin (Ne) and the output shaft rotation speed Ns. The ratio γ is obtained (block B4). Then, the input shaft sheave engagement diameter Rin at that time is obtained from the speed ratio γ (block B5).

  The input torque Tin (that is, the engine torque Te) is obtained from the input shaft rotation speed Nin (Ne) and the load factor α (block B6) (block B7). Here, since the load factor α is an index value of the engine torque related to the engine speed, for example, as indicated by the throttle opening, the input torque Tin is calculated based on the load factor α and the input shaft speed Nin (Ne). (Te) can be obtained. Further, the friction coefficient μ of the belt clamping portion is obtained from the input shaft rotation speed Nin (Ne) and the gear ratio γ (block B8).

The theoretical clamping pressure Pt, which is the clamping pressure required to prevent belt slippage,
Pt = K · Tin / (μ · Rin) · SF
Determined by Here, K is a constant, and SF is a safety factor for the clamping pressure. Accordingly, by setting the safety factor SF, the theoretical clamping pressure Pt is obtained from the input torque Tin (Te), the friction coefficient μ, and the input shaft sheave engagement diameter Rin (block B9).

The equivalent command value Duty, which is the command value when the clamping pressure decreases, is set by obtaining the calculated clamping pressure P. The calculated clamping pressure P is
P = Pt -Phard + Perror
Determined by Here, the pressure Perror corresponding to the hydraulic pressure compensation is a predetermined compensation value in consideration of, for example, temperature characteristics in the drive system and variations in the hydraulic pressure due to the effects of non-reproducibility and the like. (Block B10). The calculated clamping pressure P is determined from the pressure Perror equivalent to the hydraulic pressure compensation, the pressure Phard equivalent to the centrifugal hydraulic pressure and the spring force, and the theoretical clamping pressure Pt, and the corresponding command value Duty is set from the calculated clamping pressure P (block). B11).

  The difference ΔDuty between the actual clamping pressure command value DutyS (block B12) at the start of sliding and the equivalent command value Duty is determined, and the clamping pressure reduction equivalent ΔP, which is a value obtained by converting the ΔDuty to oil pressure, is determined (block B13). The nip pressure reduction equivalent amount ΔP is reflected in a map of “input shaft rotation speed Nin (Ne) * load ratio α * speed ratio γ”, and learning correction is performed.

  By learning and correcting the nip pressure reduction equivalent amount ΔP in this manner, variations in individual differences such as the input shaft rotation speed Nin (Ne), the load factor α, and the gear ratio γ, which are the main change factors of the limit nip pressure, are obtained. It is possible to perform an appropriate learning correction with the influence as a learning target.

  Next, a case where the clamping pressure after the map correction is set will be described with reference to FIG. First, the current output shaft speed Ns is detected (block B21). Then, a centrifugal hydraulic pressure acting on the driven pulley 14 and a pressure Phard corresponding to a spring force are obtained from the output shaft rotation speed Ns (block B22).

  The current input shaft speed Nin (Ne) is detected (block B23), and the speed ratio γ is determined from the input shaft speed Nin (Ne) and the output shaft speed Ns (block B24). Then, the current input shaft sheave engagement diameter Rin is obtained from the gear ratio γ (block B25).

  The input torque Tin (Te) is obtained from the input shaft rotation speed Nin (Ne) and the load factor α (block B26) (block B27). Further, a friction coefficient μ of the belt pressing portion is obtained from the input shaft rotation speed Nin (Ne) and the speed ratio γ (block B28), and from the speed ratio γ and the input torque Tin (Te), the driven pulley 14, ie, the output shaft The torque Ts is obtained (block B29).

  Here, based on the output shaft rotation speed Ns and the output shaft torque Ts obtained in the blocks B21 and S29, it is confirmed whether or not the current operation state is in the corrected clamping pressure use region. The corrected clamping pressure use region is, for example, a region having a predetermined upper and lower width with respect to a curve indicating a flat road load / load traveling state in a diagram in which clamping pressure is set using, for example, a vehicle speed and an output shaft torque Ts as parameters. This is a defined area. Accordingly, in this control example in which the clamping pressure is learned and corrected, the control is continuously executed when it is determined that the current running state is in the corrected clamping pressure use region. On the other hand, if it is determined that the current running state is not in the corrected clamping pressure use area, the control example is not executed.

  When the control is continuously executed, a theoretical clamping pressure Pt is determined from the input torque Tin (Te), the friction coefficient μ, and the input shaft sheave engagement diameter Rin (block B30). Further, a pressure Pakuro corresponding to the road surface input is obtained from the output shaft torque Ts (block B31). The pressure Pakuro corresponding to the road surface input is a pressure corresponding to a torque that is expected to act from the output side in accordance with the state of the road surface.

  The calculated clamping pressure P is determined from the centrifugal oil pressure, the pressure Phard corresponding to the spring force, the theoretical clamping pressure Pt, and the pressure Pakuro corresponding to the road surface input (block B32). Further, a nip pressure reduction amount ΔP is obtained from a map of “input shaft rotation speed Nin (Ne) * load ratio α * speed ratio γ” (block B33). Then, an equivalent command value Duty, which is the difference between the calculated clamping pressure P and the clamping pressure reduction equivalent amount ΔP, is output (block B34).

  In such a control example of the squeezing pressure setting, since the difference between the calculated squeezing pressure P at the start of the belt slip and the actual squeezing pressure at that time is mapped, a slight state change occurs during the detection period of the limit squeezing pressure. Even if it occurs, the detection result can be used.

  Therefore, according to the control device according to the present invention configured to execute the control shown in FIG. 1 and FIG. Since the main change factor of the amount ΔP is included in the correction, accurate learning correction is performed. In addition, when a state change from a steady state to an unsteady state occurs, or when the state is in a transitional state, the state change is reflected in the clamping pressure learning correction, and a slight state change occurs during the limit clamping pressure detection period. Can be used even if is generated. As a result, the clamping pressure can be set appropriately and accurately.

  Next, another control example executed by the control device of the present invention will be described. The control examples shown in FIGS. 4 to 9 calculate the first correction coefficient β by calculating the correlation between the theoretical clamping pressure and the limit clamping pressure when detecting the clamping pressure balanced with the input torque. A second correction coefficient β ′ obtained by further correcting the first correction coefficient β by a function of a speed ratio is obtained, and the clamping pressure is corrected by the second correction coefficient β ′ to control or set the clamping pressure. This is an example of such a configuration.

  4 to 6 are flowcharts showing one example, and FIG. 7 is a time chart when the routine shown in the flowchart is executed. The routine shown in this flowchart is repeatedly executed at predetermined short intervals. First, in FIG. 4, it is determined whether a condition for executing control for setting the clamping pressure to a relatively low pressure or so-called clamping pressure reduction control for decreasing the clamping pressure from the normal state, that is, a control start condition is satisfied. Is determined (step S101). The condition is that the torque acting on the continuously variable transmission 1 is stable, for example, that the vehicle is cruising at a medium to high speed, that the running road surface is almost flat, and that the engine speed is high. An operating area is set using parameters such as the engine load factor and the gear ratio as parameters, and learning control, which will be described later, for the operating area to which the current operating state belongs is incomplete.

  If a negative determination is made in step S101 because the control start condition is not satisfied, the flags F1, F2, and Ph are reset to zero, the stored data is cleared, and the clamping pressure is reduced or If it has been increased, the pressure is returned to the normal clamping pressure (step S113), and the process once exits this routine. The flags F1, F2, Ph will be described later.

The theoretical pinching pressure Pt (i) is a pinching pressure obtained from the input torque to the continuously variable transmission 1. Here, the input torque, the friction coefficient of the continuously variable transmission 1 and the pulleys 13 and 14 are used. The chief angle of the belt 17 is obtained as a main parameter,
Pt = Tin · cos θ / (2 · μ · Rin)
Is calculated. Here, Tin is the input torque, θ is the skew angle of the belt 17 between the pulleys 13 and 14, μ is the coefficient of friction between the pulleys 13 and 14, and the belt 17, and Rin is the winding radius of the belt 17 on the driving pulley 13. (Ie, the input shaft sheave winding radius). An estimated value is used as the input torque Tin and the friction coefficient μ, and this is one of the causes of the error in the clamping pressure. The theoretical clamping pressure Pt (i) is multiplied by a predetermined safety factor SF (> 1), and the sum of the hydraulic pressure due to the centrifugal force and the sum Phard corresponding to the pressure due to the elastic force applied to the return spring in the hydraulic actuator is subtracted from the value. An oil pressure command value Pdtgt (i) is obtained. That is,
Pdtgt (i) = Pt (i) .SF-Phard
Is calculated as

  On the other hand, if a positive determination is made in step S101 because the control start condition is satisfied, the learning area is determined (step S102). That is, the above-mentioned operation region to which the current operation state belongs is determined by parameters such as the engine speed and the engine load factor. Whether or not the learning on the squeezing pressure described below has been completed for the learning region determined in this way, that is, the region to which the current operating state belongs has already learned the squeezing pressure-related items. It is determined whether or not the area has been learned (step S103). If a negative determination is made in step S103, that is, if the learning value has not been obtained, learning control for the clamping pressure is executed.

  First, it is determined whether or not the learning area has been changed (step S104). As described above, the learning region is a region in which the engine speed, the engine load factor, the gear ratio, and the like are set as parameters, so that the learning region is operated when an accelerator pedal (not shown) is operated or when the vehicle speed changes. For example, the driving state of the vehicle changes, and when the change is large, the vehicle may fall outside the conventional learning area. In such a case, a positive determination is made in step S104.

  If an affirmative determination is made in step S104, the process proceeds to step S105, where the flags F1 and F2 are reset to zero, and the flag Ph is set to "1". The flag Ph indicates each stage (phase) of the control, and is a flag that is sequentially set from “0” before the start of the control to “4” at the end of the control. Further, a hydraulic command value Pdtgt (i) (= Pt (i) .SF-Phard) based on the theoretical clamping pressure Pt (i) obtained from the input torque at that time is obtained. Thereafter, the process proceeds to step S106. On the other hand, if a negative determination is made in step S104, the process immediately proceeds to step S106.

  In steps S106 and the subsequent steps up to step S108, the flag Ph indicating the phase is determined. That is, it is determined in step S106 whether or not the flag Ph is "4". Thereafter, in step S107, it is determined whether or not the flag Ph is "3", and in step S103, whether or not the flag Ph is "2". You. As described above, the flag Ph is set to "1" when the determination is positive in step S105, and the flag Ph remains "0" when the determination is negative. Is determined negatively in steps S106 to S108. In this case, the hydraulic pressure command value Pdtgt (i) is set to and maintained at the predetermined hydraulic pressure command value Pdstart at the start of the decrease in hydraulic pressure (step S114). This is the control in phase 1 (phase 1).

  Then, it is determined whether the predetermined time T1 has elapsed (step S115). If a negative determination is made in step S115, this routine is temporarily exited. On the other hand, if the determination is affirmative in step S115, the flag Ph indicating the phase is set to "2" (step S116), and the routine once exits. That is, the hydraulic pressure command value Pdtgt (i) is maintained at a constant value. The predetermined time T1 is a time sufficient for the actual oil pressure Pdact (i) to stabilize at a pressure corresponding to the hydraulic pressure command value Pdtgt (i). Therefore, during the predetermined time T1, the actual oil pressure Pdact (i) The relationship between i) and the hydraulic command value Pdtgt (i) based on the hydraulic command value Pdtgt (i) or the theoretical clamping pressure Pt (i) is stabilized.

  The control for maintaining the oil pressure command value Pdtgt (i) and the actual oil pressure Pdact (i) based on the command value constant is the control in the phase 1. Then, after the predetermined time T1 has elapsed and the flag Ph is set to "2", the determination in step S108 is affirmative, so that the control of phase 2 is executed. That is, the hydraulic pressure command value Pdtgt (i) is gradually reduced at a predetermined gradient ΔPdsw1 (step S109). Then, the hydraulic pressure command value Pdtgt (i), the actual hydraulic pressure Pdact (i), and the gear ratio γ (i) in the process are stored (step S110). In addition, slippage in the continuously variable transmission 1 is detected while the hydraulic pressure command value Pdtgt (i) is being reduced at a predetermined gradient ΔPdsw1 (step S111).

  The detection of slippage in the continuously variable transmission 1 can be performed by a conventionally known appropriate method. For example, the actual gear ratio γ1 at a point in time before the current time by a predetermined time Tpre1 and the predetermined time Tpre2 ( <Tpre1) The speed change ratio gradient is determined from the actual speed ratio γ2 at the previous time, and the estimated speed change γ ′ at the current time is determined based on the change gradient, and the estimated speed ratio γ ′ and the actual speed ratio γ are calculated. Can be detected when the deviation of the predetermined value exceeds a predetermined reference value. Alternatively, the slip may be detected based on the speed ratio change speed (speed ratio change rate).

  If the slip is not detected and a negative determination is made in step S111, the routine once exits to continue the previous control. Conversely, if the determination is affirmative in step S111, that is, if slippage is detected, the flag Ph is set to "3" (step S112), and the routine once exits.

  When slippage in the continuously variable transmission 1 is detected, the flag Ph is set to "3", so that the affirmative determination is made in step S107 described above. In that case, the process proceeds to step S201 of the flowchart shown in FIG. 5, and it is determined whether the flag F1 is set to "1". The flag F1 is a flag that is set to “1” to indicate that a learning value is stored in a learning area to which the current operating state belongs, and is initially “0” as described above. Is set to Therefore, a negative determination is made in step S201, and in that case, the slip start point (the time when the slip actually starts) is searched (step S202).

  As a method for the search, various conventionally known methods can be appropriately adopted. For example, two points A and B in the time chart showing the gear ratio γ in FIG. The estimated gear ratio γ ′ estimated from the gradient between the two points (between points A and B) a predetermined time before is calculated, and the estimated gear ratio γ ′ is calculated by going back to the past sequentially from the above-mentioned slip detection point. The time when the speed ratio γ is compared with the speed ratio γ and the difference exceeds a predetermined reference value can be set as the slip start time. When the slip start time is searched in this way, the theoretical clamping pressure Pt at that time, the actual oil pressure Pdreal at the start of slip, and the pressure Phard obtained by adding the pressure based on the centrifugal oil pressure and the return spring are calculated (step S203).

Then, the limit clamping pressure Ps at the time of detecting the limit clamping pressure is calculated (step S204). This is determined by adding the pressure Phard obtained by adding the pressure based on the centrifugal oil pressure and the return spring to the actual oil pressure Pdreal at the start of slip calculated in step S203. That is,
Ps = Pdreal + Phard
Is calculated by

Then, the first correction coefficient β is calculated using these values (step S205). That is, the first correction coefficient β is a correlation expressed by a ratio between the theoretical clamping pressure Pt and the limiting clamping pressure Ps at the time of detecting the limiting clamping pressure, and
β = Ps / Pt
Is calculated by

  The first correction coefficient β thus obtained is stored for each learning area (step S206). As an example, the map for the first correction coefficient β is updated. Then, the flag F1 is set to "1" (step S207).

  Subsequently, since the slip of the continuously variable transmission 1 is detected, control for converging the slip is executed. Specifically, the slip amount Δslip (i) at the time when the slip is detected is multiplied by a predetermined coefficient K1 to obtain the torque down amount Tedown (i) of the engine 5, and the torque reduction control ( For example, the ignition timing is retarded (step S208). If the flag F1 is set to "1" and the result of the determination in step S201 is affirmative, the first correction coefficient β has already been obtained and stored for each learning area. Then, steps S202 to S207 described above are skipped, the process proceeds to step S208, and the subsequent control is similarly executed.

  At the same time, the hydraulic pressure command value Pdtgt (i) is increased at a predetermined gradient Pdsw2 (step S209). The convergence of slip is detected in the course of these controls (step S210). The detection of the slip convergence can be performed by various methods. For example, it can be determined that the slip has converged when the difference between the estimated speed ratio and the actual speed ratio becomes equal to or less than a predetermined value. If a negative determination is made in step S210, the routine once exits to continue the previous control. On the other hand, if the slippage has converged and the judgment in step S210 is affirmative, the routine sets the flag Ph to "4" (step S211) to perform the control of phase 4, and then executes this routine once. Exit.

  If the slippage has converged, the flag Ph is set to "4", so that the affirmative determination is made in step S106 shown in FIG. In that case, the process proceeds to step S301 of the flowchart shown in FIG. 6, and it is determined whether or not a predetermined time T2 has elapsed. The predetermined time T2 is a time counted from the time when the determination of the slip convergence is established, and therefore, is initially determined to be negative in step S301. Subsequently, it is determined whether the flag F2 is "1" (step S302). This flag F2 is a flag that is set to “1” by executing control for stepping up the hydraulic pressure command value Pdtgt (i) by a predetermined value h, and is initially “0”. A negative determination is made in S302. In this case, control (Pdtgt (i) = Pdtgt (i-1) + h) for stepping up the hydraulic pressure command value Pdtgt (i) by a predetermined value h is executed (step S303). Then, the flag F2 is set to "1" (step S304). Thereafter, the process once exits from this routine.

  Thereafter, even if the predetermined time T2 has not elapsed, since the flag F2 is set to "1", a negative determination is made in step S301 and a positive determination is made in step S302. Therefore, in this case, the previous value Pdtgt (i-1) of the hydraulic pressure command value Pdtgt is set to the current value Pdtgt (i) (step S303). That is, the hydraulic pressure command value Pdtgt (i) is maintained at a value stepped up by the predetermined value h. In the process, the actual hydraulic pressure (clamping pressure) gradually increases. When the predetermined time T2 has elapsed, an affirmative determination is made in step S301. In this case, the flags F1 and F2 are reset to zero, the stored data is cleared (step S306), the flag Ph indicating the phase is reset to zero (step S307), and the learning of the current area is performed. The flag is turned on (step S308). Thereafter, the process once exits from this routine.

  When the learning data (first correction coefficient) β is obtained as described above, it is determined that the operation region is the learned region, and thus the determination is affirmative in step S103 shown in FIG. . In this case, the learning data β is read as the first learning data (step S117), and the speed of the continuously variable transmission 1 obtained from the input rotation speed and the output rotation speed of the continuously variable transmission 1 at that time. The gear ratio γ (i) is read (step S118).

When the first learning data β and the speed ratio γ (i) of the continuously variable transmission 1 are read, the first learning data β is shifted to reflect the effect of the change in the speed ratio γ on the setting of the clamping pressure. The second learning data β ′ corrected by the function F (γ) of the ratio γ is obtained (step S119). Then, the theoretical clamping pressure Pt (i) when the learning data is reflected is corrected using the second learning data β ′, and the clamping pressure Pt ′ (i) when the learning data is reflected is obtained (step S120). That is,
β '= β · F (γ)
Pt '(i) = Pt (i) · β'
Is calculated as corrected.

When the clamping pressure Pt '(i) when the learning data is reflected is obtained, the clamping pressure Pt' (i) when the learning data is reflected, the pressure Phard obtained by adding the pressure based on the centrifugal oil pressure and the return spring, and the road surface input correspondence The hydraulic pressure command value Pdtgt (i) is obtained from the corresponding pressure Pakuro (step S121). That is,
Pdtgt (i) = Pt '(i) -Phard + Pakuro
Is calculated as Thereafter, the process once exits from this routine.

  As described above, in the conventional method of detecting the limit clamping pressure, for example, the hydraulic pressure is gradually decreased from the hydraulic pressure corresponding to a known clamping pressure, and the hydraulic pressure immediately before the occurrence of slippage is detected as the hydraulic pressure corresponding to the limit clamping pressure. I have. Therefore, the detection result is a differential hydraulic pressure between the hydraulic pressure equivalent to the theoretical clamping pressure and the hydraulic pressure equivalent to the limiting clamping pressure obtained from the input torque when the limiting clamping pressure is detected. At this time, as in the invention of Patent Document 1 described above, the difference hydraulic pressure, which is the detection result of the above-described limit clamping pressure, is mapped on a map for each rotation speed, torque, gear ratio, temperature, or friction coefficient of the belt clamping portion. If stored, the clamping pressure can be accurately set as “theoretical clamping pressure−the stored differential oil pressure”.

  However, if many parameters (dimensions) such as the number of revolutions, torque, gear ratio, temperature, and coefficient of friction are provided in the map, the map becomes very complicated and large, which is not practical. Furthermore, if the dimension of the map is increased, the number of times of detection of the limit clamping pressure increases, so that the clamping pressure is reduced for detection, that is, the margin for slip is reduced, that is, the frequency of the so-called reduced safety factor state Will be higher. Further, even a slight slip for detection may cause a reduction in the durability of the continuously variable transmission 1. In addition, in order to simplify the map, if it is assumed that the above-described differential oil pressure is stored in the map for each rotation speed and torque, the clamping pressure is not accurately reflected due to a speed ratio or a friction coefficient that is not reflected in the map. It cannot be set well, and the safety factor against slippage of the continuously variable transmission 1 may be reduced. For example, if the deviation between the calculated value and the actual value of the friction coefficient of the belt squeezing portion accompanying the change in the speed ratio γ is large, the squeezing force cannot be set with high accuracy.

  Specifically, as shown in FIG. 8A, assuming that the actual friction coefficient μac, which is the actual friction coefficient of the belt clamping portion, is constant, the actual friction coefficient μac at the time of detecting the limit clamping force is Δμde, which is the difference between the estimated friction coefficient μes, and Δμre, which is the difference between the actual friction coefficient μac and the estimated friction coefficient μes when the learning data is reflected, have the same value. There is no problem even if there is a large change in the speed ratio γ of the continuously variable transmission 1 between the two. However, the actual friction coefficient μac of the belt squeezing portion is usually not constant due to the influence of oil deterioration or the like, and as shown in FIG. μac also changes. At this time, if the difference Δμde between the actual friction coefficient μac and the estimated friction coefficient μes at the time of detecting the limit pinching pressure is reflected as the difference ΔμH between the friction coefficient μre and the estimated friction coefficient μes at the time of learning data reflection, Since the difference between the actual friction coefficient μac and the estimated friction coefficient μes when the learning data is reflected is Δμre, an error of “ΔμH−Δμre” may occur. Then, the clamping pressure at the time of reflecting the learning data is set low due to the influence of this error, and the margin for the slip of the continuously variable transmission 1 decreases, that is, the safety factor SF may decrease.

  Therefore, as shown in FIG. 8C, in order to cope with the change in the actual friction coefficient μac, the friction coefficient μre when the learning data is reflected is corrected depending on the function F (γ) of the gear ratio γ when the learning data is reflected. By calculating the friction coefficient μco when the corrected learning data is reflected, and by reflecting the difference ΔμH ′ between the friction coefficient μco and the estimated friction coefficient μes when the corrected learning data is reflected in the setting of the clamping pressure, the clamping pressure is reduced. It is possible to prevent a reduction in the safety factor SF due to being set low.

  Note that, in the above specific example, an example is shown in which the speed ratio γ is corrected by a function F (γ) that is a function of the speed ratio γ in order to reflect the effect of the change on the setting of the clamping pressure. The learning data can be corrected by reflecting the speed ratio γ by using a correction map of the variation of the actual friction coefficient and the estimated friction coefficient due to the speed ratio γ. In addition, at this time, a function F (γ) or a correction map is set so that the slippage of the continuously variable transmission 1 is corrected on the safe side in consideration of the variation.

  Further, in the specific example shown in FIG. 8 described above, an example is described in which the deviation between the actual friction coefficient and the estimated friction coefficient at the time of detection of the limit clamping pressure is corrected, and the deviation at the time of learning data reflection is obtained and reflected in the setting of the clamping pressure. As shown in FIG. 9, the actual friction coefficient (point A) at the time of detection of the limit clamping force is calculated by using the friction coefficient (point B) when the learning data is reflected by a predetermined function of the speed ratio γ or a correction map. ), The friction coefficient when the learning data is reflected may be reflected in the setting of the clamping force.

  As described above, according to the control device of the present invention configured to execute the control shown in FIGS. 4 to 9, the change in the friction coefficient μ is obtained as a function of the speed ratio γ, and the change is reflected. By correcting the clamping force with the correction coefficient β ′, the learning map can be simplified and the clamping force control based on the limit clamping force can be easily performed. In addition, by reflecting the change in the friction coefficient μ in the clamping force control in this manner, a decrease in the safety factor SF of the continuously variable transmission 1 can be prevented or suppressed, and as a result, the belt of the continuously variable transmission 1 can be prevented. 17 and the sheaves can be improved in durability.

  Here, the relationship between the above-described specific example and the present invention will be briefly described. The functional means in steps S119 and S120 described above correspond to the learning means of the present invention.

  It should be noted that the present invention is not limited to the above specific examples, and the power transmission mechanism to which the present invention is applied is a toroidal type continuously variable transmission, a friction clutch or a friction brake in addition to the above-mentioned belt type continuously variable transmission. Or other frictional engagement means. Therefore, the "pressure" in the present invention includes the engagement pressure in addition to the clamping pressure. Further, in the above specific example, an example is shown in which the ratio between the theoretical clamping pressure and the limiting clamping pressure is used as the first correction coefficient β as a physical quantity representing the correlation between the theoretical clamping pressure and the limiting clamping pressure. In addition to this ratio, the mutual relationship may be, for example, a deviation between the theoretical clamping pressure and the limit clamping pressure. In short, the theoretical clamping pressure and the limit clamping pressure, or a relational expression obtained based on them. Any value may be used as long as it shows the relationship between the theoretical clamping pressure and the limit clamping pressure derived based on. Further, in the present invention, the state in which the relationship between the oil pressure command value and the actual oil pressure is stable is, in addition to the state in which the oil pressure command value is maintained at a constant value as described above, changes the oil pressure command value with a small gradient, The state in which the actual oil pressure is changing may be followed.

It is a block diagram for explaining an example (learning correction method) of control by the control device of the present invention. FIG. 4 is a block diagram for explaining an example of control (a squeezing pressure determination method) by the control device of the present invention. FIG. 1 is a diagram schematically illustrating an example of a drive system including a continuously variable transmission targeted by the present invention. FIG. 4 is a diagram showing a part of a flowchart for explaining an example of control by the control device of the present invention. FIG. 5 is a diagram illustrating a part that follows the flowchart illustrated in FIG. 4. FIG. 5 is a diagram showing another part following the flowchart shown in FIG. 4. 4 is a time chart showing the contents of control and changes in clamping pressure in each phase. FIG. 7 is a diagram for explaining a relationship between an actual friction coefficient and an estimated friction coefficient when a limit clamping pressure is detected, an actual friction coefficient and an estimated friction coefficient when learning data is reflected, and a gear ratio. It is a figure for explaining another example of a relation between an actual friction coefficient at the time of detection of a limit pinching pressure, an estimated friction coefficient, an actual friction coefficient at the time of learning data reflection, an estimated friction coefficient, and a gear ratio.

Explanation of reference numerals

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

Claims (5)

In the control device of the power transmission mechanism in which the transmission torque capacity changes according to the applied pressure,
A pressure setting means for setting the pressure to be applied to the power transmission mechanism by a physical quantity determined from a slip start pressure at which a slip starts when a predetermined input torque is acting and a theoretical pressure determined based on the input torque. A control device for a power transmission mechanism, comprising:   The control device for a power transmission mechanism according to claim 1, further comprising learning means for learning and correcting the physical quantity based on an operation state of the power transmission mechanism. The power transmission mechanism includes a continuously variable transmission in which a gear ratio is continuously changed and a torque capacity is changed in accordance with a clamping force, and
The power transmission mechanism according to claim 2, wherein the learning unit includes a unit that learns the physical quantity based on at least one of an input rotation speed, an input torque, and a gear ratio for the continuously variable transmission. Control device. The power transmission mechanism includes a continuously variable transmission in which a gear ratio is continuously changed and a torque capacity is changed in accordance with a clamping force, and
The control device for a power transmission mechanism according to claim 2, wherein the learning means includes means for learning and correcting the physical quantity based on a function of a speed ratio of the continuously variable transmission.   The control of the power transmission mechanism according to claim 4, wherein the learning means includes means for calculating a change in a friction coefficient in the continuously variable transmission as a function of the speed ratio and learning and correcting the physical quantity. apparatus.

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