Continuously Variable Transmission (CVT) Gear Control Device

Abstract

To provide a shift control device of a continuously variable transmission capable of suppressing generation of shock while quickly changing gear to a structural maximum or minimum gear ratio, when sudden shift request is generated.SOLUTION: In a shift control device of a continuously variable transmission including: a driving pulley and a driven pulley respectively having a movable sheave and a fixed sheave; a belt wound on a groove of each pulley; and a fixing member limiting movement of the movable sheave and setting a maximum width of the groove, and changing speed by changing a winding radius of the belt, a controller for controlling a driving power source capable of transmitting torque to the continuously variable transmission and the driving pulley, reduces the torque output by the driving power source (step S13) when the movement of the movable sheave is limited by the fixing member (step S12), in a case when the setting of a change gear ratio γmax to maximize the width of the groove is requested (step S1).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a shift control device for a belt-type continuously variable transmission that can continuously change the winding radius of a belt around a sheave and thereby continuously change the speed ratio.

Background Art

[0002] Patent Document 1 discloses a control device for a belt-type continuously variable transmission in which a sensor for detecting the supply oil pressure supplied to a hydraulic cylinder to generate a thrust on a movable sheave is provided only on the secondary pulley side. In the device of Patent Document 1, when a request to change the speed ratio occurs, the secondary pulley side slip limit thrust, which is the slip limit thrust on the secondary pulley side corresponding to the target speed ratio, and the secondary pulley side shift control thrust, which is the thrust of the secondary pulley required for shift control calculated based on the primary pulley side slip limit thrust, the larger one is selected as the target secondary thrust. And it is configured to set the target primary thrust required for shift control, which is calculated based on the target secondary thrust.

[0003] In the starting shift control device of the belt-type continuously variable transmission described in Patent Document 2, when a vehicle in a stopped state starts before the actual speed ratio in the belt-type continuously variable transmission reaches the set speed ratio (maximum speed ratio) due to sudden stop or the like, the target speed ratio actually commanded based on the actual speed ratio and the virtual target speed ratio based on the preset set speed ratio (maximum speed ratio) are calculated. And it is configured to shift the speed ratio to the Hi side based on the accelerator opening degree, and reduce the shift speed of the target speed ratio when the difference between the target speed ratio and the virtual target speed ratio becomes small.

[0004] Patent Document 3 discloses a control device configured to perform shift control in a multi-speed mode using a belt-type continuously variable transmission mechanism. In the device of Patent Document 3, in order to counteract the inertial shuttle kick that causes shock during shifting, first, the maximum torque increase or decrease that can be increased or decreased in the direction of counteracting the inertial shuttle kick, and the inertial shuttle kick that can be counteracted by this maximum torque increase or decrease are calculated based on the engine's operating state. Then, based on the inertial shuttle kick that can be counteracted, the shift speed of the continuously variable transmission at which that inertial shuttle kick occurs is set as the upper limit shift speed, and the continuously variable transmission is configured to control the shift speed so as not to exceed that upper limit shift speed.

[0005] Patent Document 4 discloses a control method that is executed when a command to perform a sudden downshift by kickdown is input to a vehicle equipped with a belt-type continuously variable transmission while speed limiting control is being performed to maintain the vehicle speed at a set speed. In the control device for the vehicle drive system described in Patent Document 4, when the above situation occurs, the speed limiting control is stopped, the target input shaft rotation speed of the continuously variable transmission is temporarily increased by an initial downshift amount, and then the rotation speed is increased to the kickdown target rotation speed at a predetermined rate of change. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5403164 [Patent Document 2] Japanese Patent Publication No. 2006-112487 [Patent Document 3] Japanese Patent Publication No. 2012-026363 [Patent Document 4] Japanese Patent Publication No. 2010-169128 [Overview of the project] [Problems that the invention aims to solve]

[0007] Each continuously variable transmission disclosed in Patent Documents 1 to 4, as described above, is configured to shift speed by adjusting the balance of frictional force (belt clamping pressure) between the belt and each sheave through thrust corresponding to the hydraulic pressure supplied to the hydraulic cylinder of the movable sheave in each pulley. For example, when downshifting, the hydraulic pressure supplied to the movable sheave in the primary pulley, which is the input side, is reduced to control the belt winding radius to be relatively small. ,tree Backdown etc. When a sudden downshift is required in a stepped transmission, the primary pulley controls the hydraulic pressure in the primary hydraulic cylinder to quickly reduce in order to immediately shift the continuously variable transmission's gear ratio to the maximum gear ratio.

[0008] As described in the patent documents mentioned above, gear changes in a continuously variable transmission (CVT) are performed by controlling hydraulic pressure to change the groove width of one of the pulleys, such as the primary pulley. For example, when downshifting, pressure is released from the primary pulley, and the belt clamping pressure from the secondary pulley widens the groove width of the primary pulley. Therefore, in the case of kick-down shifting, the gear change speed can be increased compared to upshifting. When this gear change control is performed by hydraulic feedback control, the gear change speed can be increased by increasing the deviation between the target gear ratio and the actual gear ratio. However, if the gear change speed is kept high even when the target gear ratio is reached, the gear change speed will drop sharply upon reaching the target gear ratio, which may cause a shock.

[0009] As described in the patent documents mentioned above, the shock can be avoided or mitigated by controlling the hydraulics to reduce the rate of change in the gear ratio before reaching the target gear ratio. However, reducing the gear shift speed ultimately increases the time it takes to reach the target gear ratio. Furthermore, if the gear shift ends when a movable sheave on any pulley comes into contact with a fixed member or movement restricting part provided in the mechanism to restrict its movement, the change in gear shift speed becomes particularly large. In this case, even if the shock can be mitigated by reducing the gear shift speed before the movable sheave comes into contact with the fixed member or restricting part, such a gear shift will be delayed, and it may not be possible to achieve the so-called return to the maximum gear ratio. None of the patent documents mentioned above disclose the technical problems or means for solving them when the gear shift is stopped due to the mechanism.

[0010] This invention was made in view of the above technical problems, and when a sudden gear change request occurs, the structurally optimal Big The objective is to provide a gear control device for a continuously variable transmission that can rapidly change gear ratios while suppressing the occurrence of shock at the end of the gear change. [Means for solving the problem]

[0011] To achieve the above objective, this invention provides a gear control device for a continuously variable transmission (CVT) configured to set the gear ratio by changing the winding radius of the belt on the drive pulley and the driven pulley, comprising: a drive pulley and a driven pulley, each having a movable sheave and a fixed sheave; a belt wound around a groove formed between the movable sheave and the fixed sheave of the drive pulley and the driven pulley; and a fixing member that sets the maximum width of the groove by restricting the movement of the movable sheave on the drive pulley, wherein the gear ratio is set by changing the winding radius of the belt on the drive pulley and the driven pulley, and comprising a drive force source connected to the drive pulley so as to transmit torque, and the continuously variable transmission and the The system includes a controller for controlling the drive source, and when a kickdown shift that rapidly increases the gear ratio is requested, the controller increases the gear ratio of the continuously variable transmission (CVT) by setting a virtual gear ratio that is greater than the maximum gear ratio set by setting the width of the groove of the drive pulley to the maximum width as the target gear ratio, and, provided that a kickdown shift is requested, outputs a drive torque corresponding to the driving force required by the vehicle, and when the actual gear ratio of the CVT reaches the maximum gear ratio, the movement of the movable sheave in the drive pulley is restricted by the fixed member, thereby changing the gear speed of the CVT. accompanying Nashart Change in K ,before The driving power source It is characterized by being configured to temporarily reduce the amount of luke. [Effects of the Invention]

[0012] According to the gear control device for this continuously variable transmission, in a continuously variable transmission where the gear ratio is set so that the groove width between the sheaves on the drive pulley is at its maximum width by a fixed member that limits the range of motion of the movable sheaves, when a gear ratio is requested to be set so that the groove width between the sheaves is at its maximum width on the drive pulley, the torque output by the drive power source is reduced when the gear ratio is reached. In other words, the torque of the drive power source is reduced when the movement of the movable sheaves is stopped by the fixed member and the change in the gear ratio stops. Therefore, if the change in the gear ratio is stopped abruptly or forcibly by the fixed member... It changes The inertial torque is offset by the decrease in output torque of the driving force source, which prevents or suppresses the occurrence of so-called driving force steps. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram schematically illustrates the belt-type continuously variable transmission according to the present invention. [Figure 2] This flowchart illustrates a reference example of control that can be performed by a control device for controlling a belt-type continuously variable transmission. [Figure 3] This is a time chart illustrating the changes in accelerator opening and target gear ratio when the control shown in Figure 2 is executed. [Figure 4] This is a flowchart illustrating an example of control performed by the control device in this embodiment of the invention. [Figure 5] This is a time chart illustrating the changes in accelerator opening, target gear ratio, target engine torque, and driving force when the control shown in Figure 4 is executed. [Figure 6] This flowchart illustrates other examples of control that can be performed by a control device for controlling a belt-driven continuously variable transmission. [Figure 7] This figure shows a time chart illustrating the changes in accelerator opening, target gear ratio, and differential thrust when the control shown in Figure 6 is executed.

Best Mode for Carrying Out the Invention

[0014] Hereinafter, this invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of the case where this invention is embodied, and do not limit this invention.

[0015] FIG. 1 schematically shows an example of a belt-type continuously variable transmission 1 targeted in an embodiment of this invention. The belt-type continuously variable transmission 1 shown in this FIG. 1 is configured to be able to transmit the power (torque) generated by an engine 2 used as a driving power source for traveling. For example, on the output side of the engine 2, a torque converter (fluid coupling) not shown in the drawings, a gear transmission mechanism, etc. are provided, and the belt-type continuously variable transmission 1 is connected via them. Further, on the output side of the belt-type continuously variable transmission 1, drive wheels are connected via a reduction gear device, a differential gear device, etc. not shown in the drawings. Note that this engine 2 is constituted by an internal combustion engine such as a gasoline engine or a diesel engine, for example. Also, the driving power source is not limited to the engine 2 and may be a motor or the like.

[0016] The belt-type continuously variable transmission 1 includes a primary pulley (drive pulley) 4 which is an input-side variable pulley with a variable effective diameter and is an input-side member provided on an input shaft 3, and a secondary pulley (driven pulley) 5 which is an output-side variable pulley with a variable effective diameter and is an output-side member provided on an output shaft not shown in the drawings, and a transmission belt (hereinafter also simply referred to as a belt) 6 wound between the primary pulley 4 and the secondary pulley 5. Power transmission is performed through the frictional force between the primary pulley 4, the secondary pulley 5, and the belt 6. The belt-type continuously variable transmission 1 is a transmission mechanism configured to continuously (steplessly) change the winding radius of the belt 6, that is, the speed ratio, by changing the width of the groove 7 of the primary pulley 4 and the secondary pulley 5 around which the belt 6 is wound.

[0017] The primary pulley 4 comprises a fixed sheave 4a fixed to the input shaft 3, a movable sheave 4b provided so as to be axially movable and not rotatable relative to the input shaft 3, and a primary hydraulic cylinder 4c that applies a primary thrust (= primary pressure × pressure-receiving area), which is the input thrust in the primary pulley 4, to change the width of the groove 7 between them. The secondary pulley 5 comprises a fixed sheave 5a fixed to the output shaft, a movable sheave 5b provided so as to be axially movable and not rotatable relative to the output shaft, and a secondary hydraulic cylinder 5c that applies a secondary thrust (= secondary pressure × pressure-receiving area), which is the output thrust in the secondary pulley 5, to change the width of the groove 7 between them.

[0018] The primary pressure, which is the hydraulic pressure supplied to the primary hydraulic cylinder 4c, and the secondary pressure, which is the hydraulic pressure supplied to the secondary hydraulic cylinder 5c, are independently controlled by the hydraulic control circuit 8, thereby controlling the primary and secondary thrust. As a result, the width of the grooves 7 in the primary pulley 4 and secondary pulley 5 changes, altering the belt 6's engagement diameter (effective diameter), and continuously changing the gear ratio γ (= input shaft rotation speed / output shaft rotation speed). At the same time, the frictional force (belt clamping pressure) between the primary pulley 4 and secondary pulley 5 and the belt 6 is controlled to prevent the belt 6 from slipping. In this way, the primary and secondary thrusts are controlled, allowing torque to be transmitted between the belt 6 and each pulley 4 and 5 without slippage, and setting a predetermined gear ratio. The input shaft rotation speed is the rotation speed of the input shaft 3, and the output shaft rotation speed is the rotation speed of the output shaft. The input shaft rotation speed is the same as the rotation speed of the primary pulley 4, and the output shaft rotation speed is the same as the rotation speed of the secondary pulley 5.

[0019] In the belt-type continuously variable transmission 1, for example, when the primary pressure is increased, the groove width of the primary pulley 4 is narrowed, and the gear ratio γ is reduced (i.e., the belt-type continuously variable transmission 1 is upshifted). Conversely, when the primary pressure is decreased, the groove width of the primary pulley 4 is widened, and the gear ratio γ is increased (i.e., the belt-type continuously variable transmission 1 is downshifted). Therefore, the minimum gear ratio γmin (highest speed gear ratio) is formed as the gear ratio γ of the continuously variable transmission 1 where the width of the groove 7 of the primary pulley 4 is minimized. Conversely, the maximum gear ratio γmax (lowest speed gear ratio) is formed as the gear ratio γ of the belt-type continuously variable transmission 1 where the width of the groove 7 of the primary pulley 4 is maximized. Furthermore, the belt-type continuously variable transmission 1 shown in Figure 1 is equipped with a first fixing member 9 that sets the movable range of the movable sheave 4b of the primary pulley 4, or a second fixing member 10 that sets the movable range of the movable sheave 5b of the secondary pulley 5.

[0020] The fixed members 9 and 10 are components that mechanically or structurally define the range of motion of the movable sheaves 4b and 5b in order to protect the belt-type continuously variable transmission 1. For example, the gear ratio is set by feedback control of the hydraulic pressure (groove width) of the primary pulley so that the actual gear ratio γact, which is the ratio of the actual rotational speeds of each pulley 4 and 5, becomes the target gear ratio γtgt, based on the required driving force represented by the accelerator opening and the vehicle speed. When the accelerator pedal (not shown) is pressed rapidly and heavily, the groove width of the primary pulley 4 is rapidly increased to perform a so-called kickdown shift. In this case, the movable sheave 4b on the primary pulley 4 comes into contact with the fixed member 9, so that the winding radius of the belt 6 around the primary pulley 4 does not become excessively small, and so that there is no abnormality in the winding of the belt 6 around the secondary pulley 5. In this way, the maximum gear ratio γmax is set when the winding radius of the belt 6 around the primary pulley 4 is minimized. The movement of the movable sheaves 4b and 5b can also be restricted for the movable sheave 5b in the secondary pulley 5, and the minimum gear ratio γmin is set when the movable sheave 5b is in contact with the fixed member 10 and its movement is restricted.

[0021] Belt 6 is a so-called push belt, constructed by arranging numerous elements 6a in a ring shape with their orientations aligned, and fastening them together with two ring-shaped metal hoops 6b. Each element 6a is, for example, a metal plate-like member, with both its left and right sides in the width direction inclined in a so-called V-shape when viewed from the front, and these inclined left and right sides serve as friction surfaces involved in power transmission. Belt 6 is not limited to such a push belt; it may also be a chain belt composed of multiple link plates arranged in the width direction, and rocker pins that connect these link plates so as to bend in the length direction.

[0022] The hydraulic control circuit 8 supplies oil discharged from an oil pump (not shown) to the primary pulley 4 and secondary pulley 5 via an oil passage. The hydraulic control circuit 8 also includes a primary regulator valve that adjusts the oil discharge pressure of the oil pump to the line pressure, which is the base pressure for hydraulic control of the belt-type continuously variable transmission 1; a primary pulley control valve that adjusts the hydraulic pressure (primary pressure) acting on the primary pulley 4 based on the line pressure; and a secondary pulley control valve that adjusts the hydraulic pressure (secondary pressure) acting on the secondary pulley 5 based on the line pressure.

[0023] Regarding the adjustment of the hydraulic pressure acting on the secondary pulley 5, the secondary thrust generated in the axial direction of the secondary pulley 5 based on the action of the hydraulic pressure described above is set to a value (required secondary thrust) that does not cause belt 6 slippage between the belt 6 and the primary pulley 4 and secondary pulley 5. In other words, the hydraulic pressure (secondary thrust) is adjusted to correspond to the input torque to the belt-type continuously variable transmission 1. Furthermore, regarding the adjustment of the hydraulic pressure acting on the primary pulley 4, the primary thrust generated in the axial direction of the primary pulley 4 based on the action of the hydraulic pressure described above is set to a value that makes the target gear ratio γtgt achievable. The primary pressure is configured to be controlled by feedback control, for example, the primary pressure is controlled by the deviation between the target gear ratio γtgt (or target sheave position) and the actual gear ratio γact (actual sheave position) as the control deviation.

[0024] Furthermore, as shown in Figure 1, an ECU (Electronic Control Unit) 11 is provided for controlling the engine 2, the belt-type continuously variable transmission 1, and the like. This ECU 11 corresponds to the "controller" in this embodiment of the invention and is mainly composed of a microcomputer, for example. It is configured to perform calculations using input data and pre-stored data, and to output control command signals based on the calculation results. The input data includes, for example, engine speed, input shaft speed, output shaft speed, acceleration, deceleration, accelerator opening (the amount the driver operates on the accelerator pedal), brake signals (output when the brake pedal is pressed), hydraulic signals and their rotational speeds (the hydraulic pressure supplied to each pulley 4, 5), and the axial positions of the movable sheaves 4b, 5b.

[0025] Furthermore, the output control command signals include hydraulic control command signals for controlling the belt-type continuously variable transmission 1, and the command pressure for adjusting the primary pressure (primary command pressure) and the command pressure for adjusting the secondary pressure (secondary command pressure) are output to the hydraulic control circuit 8. Specifically, the ECU 11 controls the hydraulic pressure of the secondary pulley 5 so that the belt-type continuously variable transmission 1 has a torque capacity corresponding to the input torque, and also controls the hydraulic pressure of the primary pulley 5 to achieve the target gear ratio γtgt.

[0026] In the belt-type continuously variable transmission 1 configured in this way, the gear ratio is determined based on the winding radius of the belt 6 on the primary pulley 4 side and the winding radius of the belt 6 on the secondary pulley 5 side, as described above. Torque is transmitted by the frictional force between the belt 6 and the sheave surfaces of each sheave 4a, 4b, 5a, 5b, so the hydraulic pressure of each hydraulic cylinder 4c, 5c is adjusted according to the input torque (or accelerator opening) and the target gear ratio γtgt. For example, if the vehicle requires rapid acceleration due to kickdown by the driver, and a quick downshift is required accordingly, the hydraulic pressure of the primary side hydraulic cylinder 4c may be rapidly reduced to immediately decrease the winding radius of the belt 6 on the primary pulley 4 side. However, in this belt-type continuously variable transmission 1, where the movement of the movable sheave 4b is set or restricted by the first fixing member 9, the downshift is terminated when the width of the groove 7 on the primary side is rapidly widened as described above, causing the back surface of the movable sheave 4b or the back surface of the primary side hydraulic cylinder 4c to come into contact with the first fixing member 9. When a downshift ends due to structural limitations, it is not possible to smoothly terminate the shift by overshooting the gear ratio control command value. As a result, the shift stops abruptly, the rate of change in rotational speed increases, and consequently, excessive inertia occurs. The change in Ku Occurs, and its inner shuttle The change in torque associated with the change in qThis could cause shocks when transmitted to the drive wheels. Therefore, the ECU 11 can perform a control that quickly executes a gear change while suppressing the so-called driving force step that occurs when there is a request to shift to the maximum gear ratio γmax, by rapidly changing the gear ratio of the belt-type continuously variable transmission 1.

[0027] Figure 2 is a flowchart showing an example of the control, first determining whether there is a request to downshift to the maximum gear ratio γmax (step S1). This is, as mentioned above, kickdown. etc. The system determines whether a rapid downshift is necessary to generate braking torque or prepare for restarting, in cases where rapid acceleration accompanied by an unshift is required, or conversely, when rapid deceleration is required due to sudden braking, etc. Therefore, the system is configured to make this determination based on whether, for example, the amount and speed of the accelerator pedal depression, or the amount (angle) and speed of the brake pedal depression, are greater than a predetermined threshold. If a negative determination is made in step S1 because there is no request for a downshift to the maximum gear ratio γmax, the routine in Figure 2 is terminated without executing the subsequent control. Note that in the embodiments and control examples described below, kickdown n Let's explain this assuming it's actually being executed.

[0028] If a request for downshifting to the maximum gear ratio γmax is made and this is judged positively in step S1, the process proceeds to step S2, where the target gear ratio γtgt is set to a provisional target gear ratio γint on the Hi side, which is smaller than the maximum gear ratio γmax. That is, the provisional target gear ratio γint is set so that a movable area remains, which is the gap between the primary hydraulic cylinder 4c and the first fixed member 9; in other words, the movable sheave 4b is positioned such that the primary hydraulic cylinder 4c and the first fixed member 9 do not come into contact. This provisional target gear ratio γint may be any predetermined gear ratio, or it may be set each time according to the gear ratio at which the shift to the maximum gear ratio γmax is initiated. Once the provisional target gear ratio γint is set, the process proceeds to step S3.

[0029] In step S3, it is determined whether the actual gear ratio γact has reached the provisional target gear ratio γint set in step S2. The actual gear ratio γact is calculated based on the rotational speed or rotational speed of the input shaft 3 connected to the primary pulley 4 and the output shaft of the engine 2, as well as the rotational speed or rotational speed of the output shaft connected to the secondary pulley 5, detected by sensors, for example. Alternatively, it can be calculated based on the sheave position on each pulley, the belt engagement diameter on each pulley, etc., and it is determined whether the actual gear ratio γact has reached the provisional target gear ratio γint by comparing the calculated actual gear ratio γact with the provisional target gear ratio γint. If it is determined negatively in step S3 because the actual gear ratio γact has not reached the provisional target gear ratio γint, the control in steps S2 and S3 is repeatedly executed until the actual gear ratio γact reaches the provisional target gear ratio γint.

[0030] Conversely, if a positive determination is made in step S3 because the actual gear ratio γact has reached the provisional target gear ratio γint, the process proceeds to step S4, where the target gear ratio γtgt is set to a virtual gear ratio γexc that is lower than the maximum gear ratio γmax, compared to the provisional target gear ratio γint. In step S4, because the actual gear ratio γact has reached the provisional target gear ratio γint in step S3, the belt-type continuously variable transmission 1 is controlled to shift gears up to the maximum gear ratio γmax that should ultimately be set. That is, the hydraulic pressure of the primary-side hydraulic cylinder 4c is controlled so that the winding radius (width of the groove 7) of the primary pulley 4 is maximized. In this control example, by setting the target gear ratio γtgt to a virtual gear ratio γexc that is greater than the maximum gear ratio γmax, the primary-side movable sheave 4b is pressed against the first fixed member 9 to ensure that the actual gear ratio γact is set to the maximum gear ratio γmax. This control is terminated by setting the target gear ratio γtgt to a lower value than the maximum gear ratio γmax.

[0031] Next, Figure 3 shows the changes in the target gear ratio γtgt and the actual gear ratio γact when the control described in Figure 2 is performed. As shown in Figure 3, when driving with a constant accelerator opening... 、t At a given point in time, the throttle opening increases rapidly. When this is done, kickdown etc. will be executed. To satisfy the driving force and vehicle speed based on the accelerator opening, the target gear ratio γtgt is gradually increased as a transient target value for the gear ratio during shifting. In this control example, the target gear ratio γtgt is increased at a predetermined rate of change toward a provisional target gear ratio γint that is temporarily set to be smaller than the structural maximum gear ratio γmax of the belt-type continuously variable transmission 1, that is, to the extent that the primary hydraulic cylinder 4c and the first fixed member 9 do not come into contact. Control is also initiated to increase the actual gear ratio γact in accordance with the change in the target gear ratio γtgt. As described above, shifting in the belt-type continuously variable transmission 1 is performed by adjusting the primary pressure, which is the hydraulic pressure supplied to each pulley 4. That is, in downshifting, the primary control valve is driven and controlled to release pressure from the primary pulley 4, and the primary pressure is adjusted to correspond to the target gear ratio γtgt.

[0032] At time t2, the target gear ratio γtgt reaches the provisional target gear ratio γint, temporarily interrupting the change in the target gear ratio γtgt. At this time, due to unavoidable delays in the execution of gear shifting, such as hydraulic control delays, the actual gear ratio γact changes to follow the change in the target gear ratio γtgt, as shown by the dotted line in Figure 3. The shifting speed of the actual gear ratio γact then increases quadratically, and at time t3, the actual gear ratio γact reaches the provisional target gear ratio γint. The timing at which the actual gear ratio γact reaches the provisional target gear ratio γint can be predicted by the rotational speed of each pulley 4 and 5.

[0033] At time t3, it is detected that the actual gear ratio γact has reached the provisional target gear ratio γint, and the target gear ratio γtgt is set again to a larger gear ratio. The target gear ratio γtgt set at this time is set to a virtual gear ratio γexc that is lower than the structurally maximum gear ratio γmax, i.e., greater than the maximum gear ratio γmax. With the virtual gear ratio γexc set, the target gear ratio γtgt becomes larger at a predetermined shift speed. Furthermore, for example, feedforward control is configured so that when the actual gear ratio γact reaches the provisional target gear ratio γint at time t3, the change in the actual gear ratio γact does not stagnate and the shift continues.

[0034] At time t4, when the target gear ratio γtgt reaches the structurally maximum gear ratio γmax, the actual gear ratio γact also reaches the structurally maximum gear ratio γmax almost simultaneously. The shift speed of the target gear ratio γtgt from time t3 to t4 is slower than the shift speed of the target gear ratio γtgt from time t1 to t2, and therefore the actual gear ratio γact changes in line with the target gear ratio γtgt. Subsequently, the target gear ratio γtgt is shifted to the virtual gear ratio γexc, which is reached at time t5. Furthermore, even after the primary hydraulic cylinder 4c and the first fixed member 9 come into contact, the actual gear ratio γact is pressed against the first fixed member 9, completing the shift to the maximum gear ratio γmax.

[0035] As described above, in this control example, when a sudden downshift such as a kickdown is required, the target gear ratio γtgt is set to a virtual gear ratio γexc that is greater than the maximum gear ratio γmax, via a temporary gear ratio called the provisional target gear ratio γint. Consequently, the actual gear ratio γact is shifted rapidly to the provisional target gear ratio γint, and then shifted relatively slowly to the structurally maximum gear ratio γmax. Therefore, when a sudden downshift is required, the actual gear ratio γact increases quadratically to the provisional target gear ratio γint, as shown in Figure 3, and then shifts relatively slowly in line with the change in the target gear ratio γtgt, without the change in the actual gear ratio γact stagnating, up to the structurally maximum gear ratio γmax. In other words, it rapidly downshifts to the maximum gear ratio γmax while suppressing a rapid change in the rate of change of the actual gear ratio γact. Therefore, the inner shuttle is affected by the rapid change in the rate of change of the actual gear ratio γact. The change in Ku This can prevent a sudden, temporary surge in driving force, thereby suppressing or preventing shocks from occurring in the vehicle.

[0036] Next, an embodiment of this invention will be described with reference to Figure 4. As described above, when performing a kickdown, the required driving force based on the accelerator opening and vehicle speed is supplied. Add This increases engine torque. On the other hand, once the downshift is complete... ,strange Inner shuttle caused by the abrupt end of speed Depending on the change in , A temporary increase in driving force can result in a shock to the vehicle. Therefore, the embodiment described in Figure 4 uses engine torque to control the inner shuttle. The torque equivalent to the change in q This embodiment is configured to downshift more quickly while offsetting. Steps similar to those in the control example shown in Figure 2 above are given the same step numbers, and the explanation of the content of those steps is omitted or simplified.

[0037] First, as described above, step S1 determines whether or not there is a request to downshift to the maximum gear ratio γmax. If the determination in step S1 is negative because there is no request to downshift to the maximum gear ratio γmax, this flow is terminated without executing the subsequent control. Conversely, kickdown ni Therefore, if a request for a downshift to the maximum gear ratio γmax is made and judged positively in step S1, the process proceeds to step S12.

[0038] In step S12, it is determined whether the actual gear ratio γact is approaching the maximum gear ratio γmax. This is determined, for example, by whether the difference between the actual gear ratio γact and the maximum gear ratio γmax is within a predetermined range, or whether the actual gear ratio γact has reached a predetermined gear ratio. Alternatively, it may be determined based on the rotational speed of the primary pulley 4 and its axial position, and the values ​​of these when the actual gear ratio γact reaches the maximum gear ratio γmax, or by prediction based on the change in the actual gear ratio γact. If it is determined negatively in step S12 because the actual gear ratio γact is not approaching the maximum gear ratio γmax, step S12 is repeated until the actual gear ratio γact approaches the maximum gear ratio γmax.

[0039] Conversely, if the actual gear ratio γact approaches the maximum gear ratio γmax, and a positive judgment is made in step S12, the process proceeds to step S13. In step S13, when downshifting is performed, the engine torque output for acceleration is reduced, and the engine torque is controlled to return to its original output with a sweep. That is, just before or almost simultaneously with the completion of the downshift to the maximum gear ratio γmax, the inert shuttle The torque equivalent to the change in q cancel each other out so The engine torque is temporarily reduced. Then, upon completion of the shift to the maximum gear ratio γmax, the engine torque output is rapidly increased, returning to the original engine torque magnitude based on the throttle opening, etc. After that, the flow ends as the engine torque returns to the output before the temporary reduction.

[0040] Next, Figure 5 shows the changes in the target gear ratio γtgt and target engine torque when the control described in Figure 4 is performed. As shown in Figure 5, while driving with a constant accelerator opening, at time t11... te A The accelerator opening is rapidly increasing When this is done, kickdown etc. will be executed. To satisfy the driving force (vehicle acceleration G) and vehicle speed based on the accelerator opening, the target gear ratio γtgt and target engine torque increase. On the other hand, the actual gear ratio γact does not change immediately due to delays, as mentioned above, but gradually increases quadratically (or with a first-order lag). Until the downshift actually begins, the vehicle's driving force begins to increase along with the increase in engine torque. At time t12, the target engine torque becomes constant because it has become the engine torque required based on the accelerator opening, etc., and accordingly, the output of the actual engine torque also becomes constant.

[0041] At time t13, the delayed downshift of the actual gear ratio γact begins, and the rotational speed of the primary pulley 4 increases due to a portion of the output torque of engine 2. Therefore, as shown by the dashed line in Figure 5 along the change in driving force, the rotational speed increase due to the gear shift Yoru ISince the driving force decreases by the amount of Nasha, the magnitude of the driving force becomes almost constant from time t13 onwards.

[0042] Subsequently, at time t14, the target gear ratio γtgt reaches a virtual gear ratio γexc that is greater than the maximum gear ratio γmax. Then, at time t15, the actual gear ratio γact, which had been increasing in line with the target gear ratio γtgt, shifts up to the structurally maximum gear ratio γmax. Furthermore, feedforward control is used to rapidly reduce the target engine torque in accordance with the timing when the actual gear ratio γact reaches the maximum gear ratio γmax. As a result, the actual engine torque also decreases rapidly in accordance with the target engine torque, thus reducing the inertial shuttle. The torque equivalent to the change in q The decrease in engine torque offsets this, and the vehicle's driving force remains almost unchanged around the t15 point.

[0043] Subsequently, at time t16, after a predetermined time has elapsed since the shift to the maximum gear ratio γmax was completed, the target engine torque is rapidly increased to time t17 without causing a shock to the vehicle, and controlled to return to an engine torque corresponding to the accelerator opening. At this time, the rate of increase of the target engine torque from time t16 to time t17 is lower than the rate of increase from time t11 to time t12. Also, from time t16 onward, since the shift is complete, the driving force of the vehicle increases in accordance with the increase in the output torque of engine 2.

[0044] As described above, in this embodiment, the output torque of engine 2 is temporarily reduced when the actual gear ratio γact reaches the maximum gear ratio γmax. Then, after a predetermined time has elapsed, it is swept back up to the original engine torque. Therefore, when the shift to the maximum gear ratio γmax is completed, the downshift ends abruptly due to structural constraints. evening Because the engine torque decreases by the amount of inertia shuttle shift, when the gear change is complete the inertia shuttle shifts Changes in theThis can suppress the resulting sudden surge in driving force. Therefore, according to the embodiments shown in Figures 4 and 5, it is possible to suppress or avoid shocks to the vehicle caused by shifting to the maximum gear ratio γmax accompanied by a sudden downshift such as kickdown. Furthermore, since the shift speed of the actual gear ratio γact is not changed, the inner shuttle Changes in the This suppresses the occurrence of shocks and allows for rapid downshifting to the maximum gear ratio γmax as required.

[0045] Next, with reference to Figure 6, other control examples that can be performed by the ECU11 described above will be explained. As mentioned above, the inert shuttle responds to the rapid decrease in shift speed after the gear shift is completed. Changes in the Therefore, a shock occurs. In other words, if a sudden decrease in the shift speed can be prevented, the shock can be suppressed. Thus, the control example shown in Figure 6 shows a control configuration in which, when a sudden downshift is requested, the shift speed of the actual shift ratio γact is directly adjusted without changing the target shift ratio γtgt, and the gear shift is changed up to the maximum shift ratio γmax. Note that steps similar to those in the control examples in Figures 2 and 4 above are given the same step numbers, and the explanation of the content of those steps is omitted or simplified.

[0046] First, as described above, in step S1, it is determined whether or not there is a request to shift to the maximum gear ratio γmax. If the determination in step S1 is negative because there is no request to shift to the maximum gear ratio γmax, the process ends without executing any further control. Conversely, if the determination in step S1 is positive because there is a request to shift to the maximum gear ratio γmax, the process proceeds to step S22.

[0047] In step S22, it is determined whether the actual gear ratio γact is greater than or equal to a predetermined gear ratio γpre. This predetermined gear ratio γpre may be any predetermined gear ratio, and is a gear ratio close to the maximum gear ratio γmax, taking into account the hydraulic response and shift speed mentioned above. Alternatively, the predetermined gear ratio γpre may be a gear ratio suitable according to the gear ratio at the start of shifting. In other words, it is sufficient if the gear ratio allows the actual gear ratio γact to smoothly reach the maximum gear ratio γmax, taking into account control delays and shift speed. If the actual gear ratio γact is less than the predetermined gear ratio γpre, and the determination in step S22 is negative, the process returns, and this determination step is repeated until the actual gear ratio γact is greater than or equal to the predetermined gear ratio γpre. Conversely, if the actual gear ratio γact is greater than or equal to the predetermined gear ratio γpre, and the determination in step S22 is positive, the process proceeds to step S23.

[0048] In step S23, the differential thrust in the belt-type continuously variable transmission 1 is reduced to decrease the shift speed. As described above, when changing the gear ratio of the belt-type continuously variable transmission 1, the gear ratio is changed by increasing or decreasing the hydraulic pressure supplied to each hydraulic cylinder 4c and 5c, thereby changing the balance of the thrust generated on each pulley 4 and 5 and changing the winding radius of each pulley 4 and 5. For example, when rapidly downshifting, the differential thrust, which is the thrust that is subtracted (or added) from the current thrust generated on the primary pulley 4, is set to a large value in the direction of decreasing the generated thrust. In this step S23, the differential thrust, which was set to a large value for rapid downshifting, is controlled to decrease just before the actual gear ratio γact reaches the maximum gear ratio γmax. The differential thrust to be reduced at this time is set taking into account control delays such as hydraulic pressure, and is set to a value that allows the shift speed to decrease smoothly. Furthermore, the system may be configured to reduce the differential thrust by feedforward control or by reducing the feedback gain. The shifting is then continued with the reduced differential thrust, and this process ends when the actual gear ratio γact reaches the maximum gear ratio γmax.

[0049] Next, Figure 7 shows the changes in the target gear ratio γtgt and differential thrust when the control described in Figure 6 is performed. As shown in Figure 7, while driving with a constant throttle opening, kickdown occurs at time t21. etc.When the accelerator opening increases rapidly, the target gear ratio γtgt increases in order to satisfy the driving force and vehicle speed based on that accelerator opening. Accordingly, the differential thrust is increased, and the thrust generated on the primary pulley 4 side is reduced. As mentioned above, a rapid downshift is required, so the differential thrust also increases rapidly, and at t22, the differential thrust reaches the structurally maximum differential thrust. Even if the differential thrust is increased rapidly in accordance with the change in the target gear ratio γtgt, the actual gear ratio γact does not change immediately due to delays, etc., and the shift speed increases quadratically (or with a first-order lag). The target gear ratio γtgt changes at a predetermined shift speed and reaches a virtual gear ratio γexc that is greater than the maximum gear ratio γmax at t23.

[0050] Then, at time t24, control is initiated to reduce the differential thrust when the actual gear ratio γact reaches a predetermined gear ratio γpre. In other words, feedforward control is used to reduce the differential thrust by a predetermined amount in accordance with the timing when the actual gear ratio γact reaches a predetermined gear ratio γpre. The predetermined gear ratio γpre is, as mentioned above, a gear ratio smaller than the maximum gear ratio γmax, and is a gear ratio that takes into account, for example, the shift speed of the actual gear ratio γact. The amount of differential thrust to be reduced is such that the shift of the actual gear ratio γact becomes smooth, and is determined by taking into account the shift speed when the actual gear ratio γact reaches the maximum gear ratio γmax.

[0051] At time t25, once the control to reduce the differential thrust by the amount set in this manner is complete, the differential thrust is then gradually reduced until it becomes 0 at time t26. Furthermore, the actual gear ratio γact continues to downshift relatively slowly from time t24 onward based on the reduced differential thrust, reaching the maximum gear ratio γmax at time t26, after which the control to press against the first fixed member 9 as described above is executed. Note that the control to reduce the differential thrust to 0 may be performed by feedforward control, or the control may be terminated when the primary pressure decreases to approximately 0.

[0052] In the control example explained using Figures 6 and 7, a predetermined gear ratio γpre is set so that the actual gear ratio γact is smaller than the maximum gear ratio γmax, and the differential thrust is reduced when the actual gear ratio γact reaches that predetermined gear ratio γpre. As a result, the shift speed of the actual gear ratio γact is also reduced by the amount by which the differential thrust is reduced. In other words, the actual gear ratio γact shifts smoothly, and the shift speed decreases quadratically until it reaches the maximum gear ratio γmax. As a result, compared to the case where the actual gear ratio γact reaches the maximum gear ratio γmax without reducing the differential thrust, when the maximum gear ratio γmax is reached... ni This makes it possible to suppress a temporary increase in power. Therefore, it is possible to suppress or avoid the occurrence of shocks in the vehicle due to so-called driving force steps. In addition, in this embodiment, since it is not necessary to change the target gear ratio γtgt, the control can be configured using the conventional target gear ratio γtgt.

[0053] The embodiments and control examples of this invention have been described above, but this invention is not limited to the examples described above, and may be modified as appropriate within the scope of achieving the objective of this invention. 。 [Explanation of symbols]

[0054] 1. Belt-type continuously variable transmission 2. Engine (power source) 3 Input axes 4. Primary pulley (drive pulley) 4a Fixed sheave 4b Movable sheave 4c Primary side hydraulic cylinder 5. Secondary pulley (driven pulley) 5a Fixed sheave 5b Movable sheave 5c Secondary hydraulic cylinder 6 belts 7 grooves 8. Hydraulic control circuit 9. First fixing member 10 Second fixing member 11 ECU (Controller)

Claims

[Claim 1] A gear control device for a continuously variable transmission, comprising a drive pulley and a driven pulley each having a movable sheave and a fixed sheave, a belt wound around a groove formed between the movable sheave and the fixed sheave of the drive pulley and the driven pulley, and a fixing member that sets the maximum width of the groove by restricting the movement of the movable sheave in the drive pulley, wherein the gear ratio is set by changing the winding radius of the belt in the drive pulley and the driven pulley, A drive force source connected to the drive pulley so as to transmit torque, The system comprises a continuously variable transmission and a controller for controlling the power source, The aforementioned controller, When a kickdown shift that rapidly increases the gear ratio is required, the gear ratio of the continuously variable transmission is increased by setting a virtual gear ratio that is greater than the maximum gear ratio set by setting the width of the groove of the drive pulley to the maximum width, and using this as the target gear ratio. Conditional on the aforementioned kickdown shift being requested, the system outputs a drive torque corresponding to the driving force required by the vehicle, and when the actual gear ratio of the continuously variable transmission reaches the maximum gear ratio, the torque of the drive source is temporarily reduced by the amount of change in the inertia shuttle due to the change in the gear shift speed of the continuously variable transmission caused by the restriction of the movement of the movable sheave in the drive pulley to the fixed member. A gear shift control device for a continuously variable transmission, characterized by being configured as follows.

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