Control device for a continuously variable transmission of a vehicle

Abstract

The present application aims to prevent the ratio (transmission ratio) of a continuously variable transmission from being shifted to the lower side (low speed side) in the event of a defect such as a failure of a rotation number sensor of the continuously variable transmission. A control device for a continuously variable transmission of a vehicle includes an oil pressure supply device (46) that supplies oil pressure applied to a driving pulley (26a) of a continuously variable transmission (26), and a control device (90) that controls the supply of oil pressure by the oil pressure supply device (46), the control device for the continuously variable transmission of the vehicle performing feedback control of the oil pressure so that an actual transmission ratio of the continuously variable transmission (26) calculated on the basis of a detected value of a rotation number sensor (72) becomes a target transmission ratio, and performing transmission ratio feedback gain reduction control to set a value of a feedback gain of the transmission ratio in the feedback control to be smaller than a value in a case where the actual transmission ratio is greater than a prescribed transmission ratio.

Description

Technical Field

[0001] This invention relates to a control device for a continuously variable transmission (CVT) for vehicles, which consists of a power transmission component such as a metal chain or belt wound between the driving wheel and the driven wheel. Background Technology

[0002] The vehicle is configured such that the output from the drive wheels is changed and transmitted to the drive wheels via a transmission. As a transmission, for example as shown in Patent Document 1, a continuously variable transmission (CVT) is well known, comprising a belt mechanism consisting of a drive-side pulley and a driven-side pulley with variable wheel width, on which an annular belt is wound. The transmission changes the pulley width by controlling the hydraulic pressure supplied to the drive-side pulley and the driven-side pulley, thereby changing the winding radius of the belt on the pulley, and thus continuously changing the controlled gear ratio. A control device is provided in the vehicle including such a transmission to control the hydraulic pressure according to the vehicle's condition, thereby controlling the operation of the transmission.

[0003] [Existing technical documents]

[0004] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-45709 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] In the control device of the continuously variable transmission (CVT) with the aforementioned structure, the oil pressure supplied to the CVT is controlled based on the detection values ​​of a speed sensor that detects the rotational speed of the CVT's drive-side and driven-side pulleys. However, if the speed sensor fails to output a normal detection value due to malfunction or other defects, it may hinder the CVT's shift control; therefore, it is necessary to properly determine the malfunction of the speed sensor.

[0008] Conventional methods for diagnosing malfunctions in continuously variable transmissions (CVTs) involve detecting the difference between the rotational speed of the turbine in the torque converter located on the input side of the CVT and the rotational speed of rotating components such as gears located on the output side. If the difference is not within the normal range, the malfunction is identified as a faulty tachometer. However, this method requires a certain amount of time before a malfunction is identified, and during this time, gear control may be performed based on the detection value of the malfunctioning tachometer, potentially leading to temporary miscontrol conditions such as the CVT's gear ratio becoming too low.

[0009] Furthermore, as another method for determining the fault of the CVT's speed sensor, it is also considered to use the detection values ​​of other speed sensors that detect the speed of rotating elements other than gears or shafts in the CVT for CVT shift control. However, in such cases, if there is a clutch or the like between the CVT and other rotating elements, the detection values ​​of other speed sensors may not accurately reflect the current speed of the CVT if the engagement state of the clutch is unclear. Therefore, there is a risk that the method may not be usable.

[0010] Furthermore, we are also considering adding other speed sensors to the system in case of unexpected failure of the speed sensor. However, this may increase the cost or weight of the vehicle due to the addition of speed sensors.

[0011] This invention was made to solve the aforementioned problem, and its purpose is to provide a control device for a continuously variable transmission (CVT) that can maintain proper control of the gear ratio of the CVT even in the event of defects such as a malfunction of the CVT's speed sensor, using a relatively simple structure and control.

[0012] [Technical means to solve the problem]

[0013] To address the aforementioned issues, the control device for a continuously variable transmission (CVT) for vehicles according to the present invention includes: a CVT 26 comprising a drive wheel 26a that transmits driving force from a drive source 10 of the vehicle and rotates therein, a driven wheel 26b that transmits the driving force associated with the rotation to the output side, and a power transmission member 26c wound between the drive wheel 26a and the driven wheel 26b, which continuously changes the rotational speed of the drive wheel 26a and transmits the power to the driven wheel 26b by changing the wheel width of the drive wheel 26a and the driven wheel 26b; a rotational speed sensor 72 that detects the rotational speed of the drive wheel 26a or the driven wheel 26b; and a hydraulic supply unit. The system includes a hydraulic supply device 46 for supplying hydraulic pressure to the drive wheel 26a, and a control device 90 for controlling the supply of hydraulic pressure via the hydraulic supply device 46. The control device 90 performs feedback control of the hydraulic pressure in such a way that the actual gear ratio of the continuously variable transmission 26 calculated based on the detection value of the speed sensor 72 becomes the target gear ratio. If the actual gear ratio is below a specified gear ratio, the system performs gear ratio feedback gain reduction control, setting the value of the gear ratio feedback gain in the feedback control to be less than the value when the actual gear ratio is greater than the specified gear ratio.

[0014] In the control device of a continuously variable transmission (CVT) for vehicles, when the actual gear ratio is below the specified gear ratio, there is a risk of defects such as the malfunction of the speed sensor that detects the rotational speed of the driving or driven wheel of the CVT. However, according to the present invention, in this case, by performing gear ratio feedback gain reduction control, the value of the gear ratio feedback gain in the feedback control is set to be less than the value when the actual gear ratio is greater than the specified gear ratio, which can prevent the CVT ratio from shifting to an excessively low (low-speed) ratio.

[0015] Furthermore, the control device for a continuously variable transmission (CVT) for vehicles according to the present invention can properly determine defects such as malfunctions of the rpm sensors without increasing the number of rpm sensors or performing complex control, thereby preventing the CVT ratio from shifting to an excessively low ratio. Therefore, it can suppress the increase in vehicle cost, and even in the event of an abnormality such as a rpm sensor malfunction, it can ensure the stability of vehicle behavior until the vehicle stops at a safe location.

[0016] Furthermore, in the control device of the continuously variable transmission (CVT) for vehicles, the specified gear ratio can be the smallest gear ratio structurally achievable by the CVT 26, or a smaller gear ratio. Additionally, as an example, the smallest structurally achievable gear ratio of the CVT described herein can be the gear ratio at the OD end of the CVT in the embodiments described below.

[0017] According to the aforementioned structure, by setting the specified gear ratio to the minimum structurally achievable gear ratio of the continuously variable transmission (CVT), the likelihood of defects such as malfunction of the speed sensor is high when the actual gear ratio is below the specified gear ratio. Therefore, it is possible to properly determine whether a defect such as a speed sensor malfunction has occurred and to perform gear ratio feedback gain reduction control, thereby ensuring the stability of vehicle behavior until the vehicle comes to a safe stop.

[0018] Furthermore, in the control device of the continuously variable transmission for vehicles, the control device 90 may have a target gear ratio mapping for obtaining the target gear ratio. In the case where the target gear ratio on the target gear ratio mapping is in the region of a gear ratio that is not used in control and is a gear ratio that is larger than the smallest gear ratio that the continuously variable transmission 26 can structurally obtain, the gear ratio feedback gain reduction control is performed.

[0019] According to the aforementioned structure, in the region where the target gear ratio on the target gear mapping is a gear ratio not used in control and is smaller than the smallest gear ratio structurally achievable by a continuously variable transmission (CVT), the likelihood of defects such as malfunction of the rev sensor is high. Therefore, by properly identifying defects such as malfunction of the rev sensor and performing gear ratio feedback gain reduction control, the stability of vehicle behavior can be ensured until the vehicle comes to a safe stop.

[0020] Furthermore, the control device for the continuously variable transmission (CVT) for the vehicle may include: a vehicle speed detection component 76 for detecting the vehicle speed V; an accelerator operating element 56 for operation by the driver of the vehicle; and an accelerator opening detection component 56a for detecting the accelerator opening AP caused by the operation of the accelerator operating element 56, wherein the regions S1 and S2 of the gear ratios not used in the target gear shift mapping are set based on the accelerator opening AP and the vehicle speed V.

[0021] Furthermore, the regions S1 and S2 of the gear ratios that are not used in the control of the target gear mapping can be regions below the gear ratios when the accelerator opening AP is essentially in a fully closed state.

[0022] Furthermore, the control device for the continuously variable transmission (CVT) for the vehicle includes a torque converter 24 with a lock-up clutch 24c. The torque converter 24 with the lock-up clutch 24c is mounted on the vehicle. When the vehicle speed is below a specified vehicle speed V1 and the lock-up clutch 24c is closed, the region S1 of the gear ratios that are not used in the target gear shift mapping is set by the value of the accelerator opening AP and the vehicle speed V in the target gear shift mapping based on the state in which the lock-up clutch 24c is open.

[0023] When the vehicle speed is below the specified speed, the lock-up clutch of the torque converter is closed. This could potentially cause a temporary change in the input RPM of the continuously variable transmission (CVT), i.e., the RPM of the drive wheels (gear ratio). Therefore, when the vehicle speed is below the specified speed and the lock-up clutch is closed, by setting a range of unused gear ratios in the target gear ratio mapping based on the accelerator opening and vehicle speed with the lock-up clutch open, the system can avoid being affected by the temporary change in the RPM of the drive wheels caused by the lock-up clutch being closed. This allows for the proper identification of defects such as RPM sensor malfunctions.

[0024] Furthermore, the control device for the continuously variable transmission (CVT) of the vehicle may include a low friction coefficient road determination component, which determines whether the friction coefficient of the road surface on which the vehicle is traveling is a low friction coefficient road below a specified value. If the control device 90 determines that the road surface on which the vehicle is traveling is a low friction coefficient road using the low friction coefficient road determination component, it will not perform the gear ratio feedback gain reduction control.

[0025] When a vehicle is traveling on a low-friction surface, wheel slippage can cause sudden changes in wheel speed, vehicle speed, or acceleration. This can lead to temporary changes in the continuously variable transmission (CVT) speed (gear ratio) detected by the speed sensor. Therefore, by not implementing gear ratio feedback gain reduction control when the vehicle is traveling on a low-friction surface, the system can avoid being affected by temporary CVT speed changes caused by the low-friction surface and can accurately identify defects such as speed sensor malfunctions.

[0026] Furthermore, the symbols within the parentheses are symbols that illustrate structural elements in the embodiments described below as examples of the present invention.

[0027] [The effects of the invention]

[0028] The control device for a continuously variable transmission (CVT) for vehicles according to the present invention can maintain proper control of the CVT's gear ratio even in the event of a defect such as a malfunction in the CVT's speed sensor, using a relatively simple structure and control. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating an overall structural example of a vehicle including a control device for a continuously variable transmission (CVT) according to an embodiment of the present invention.

[0030] Figure 2 This is the hydraulic circuit diagram of the hydraulic supply mechanism.

[0031] Figure 3 This is a block diagram representing the transmission control system of a CVT (Continuously Variable Transmission).

[0032] Figure 4 This is a time series diagram showing the time-varying changes of various values ​​under the conditions of not implementing variable ratio feedback gain reduction control and implementing variable ratio feedback gain reduction control.

[0033] Figure 5 It is a diagram representing the target gear ratio mapping used to obtain the target gear ratio.

[0034] [Explanation of Symbols]

[0035] 1: Automatic transmission

[0036] 10: Engine

[0037] 12: Drive wheels

[0038] 16: DBW Organization

[0039] 20: Injector

[0040] 22: Crankshaft

[0041] 24: Torque converter

[0042] 24a: Pump impeller

[0043] 24b: Turbine rotor

[0044] 24c: Lock-up clutch

[0045] 26: Transmission mechanism (CVT)

[0046] 26a: Drive wheel

[0047] 26b: Driven wheel

[0048] 26c: Belt (power transmission component)

[0049] 28: Forward / Reverse Switching Device

[0050] 32: Differential gear

[0051] 44: Gear selector

[0052] 44a: Gear selector switch

[0053] 46: Hydraulic supply mechanism

[0054] 50: Engine RPM sensor

[0055] 54: Throttle valve opening sensor

[0056] 56: Accelerator pedal

[0057] 56a: Accelerator opening sensor

[0058] 66: Engine controller

[0059] 70: NT sensor (rotation sensor)

[0060] 72: NDR sensor (rotation sensor)

[0061] 74: NDN sensor (rotation sensor)

[0062] 76: Vehicle speed sensor

[0063] 82: Oil pressure sensor

[0064] 84: Oil temperature sensor

[0065] 90: Gear shift controller

[0066] MS: Spindle

[0067] CS: Sub-shaft

[0068] SS: Second Axis

[0069] M1: Target Gear Ratio Determiner

[0070] M2: Variable speed ratio feedback PID control

[0071] M3: Gear ratio feedback gain reduction control execution judgment unit Detailed Implementation

[0072] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 This is a schematic diagram illustrating the overall structure of a vehicle including a control device for a continuously variable transmission (CVT) according to an embodiment of the present invention. The vehicle shown in the figure includes an engine (internal combustion engine) 10 as a drive source, a torque converter 24 with a lock-up clutch 24c, and an automatic transmission 1 including a continuously variable transmission (CVT) 26 that outputs the rotational speed change caused by the driving force of the engine 10, and a forward / reverse switching device 28. The forward / reverse switching device 28 includes a forward clutch 28a provided for disconnecting and connecting the transmission of the driving force of the engine 10 to the transmission mechanism 26. Furthermore, the vehicle includes an engine controller 66 and a shift controller 90 as control devices for controlling the engine 10, the transmission mechanism 26, and the forward / reverse switching device 28.

[0073] A throttle valve (not shown) configured in the intake system of engine 10 is connected to a drive-by-wire (DBW) mechanism 16 and is switched by the DBW mechanism 16, which includes an actuator such as an electric motor that disconnects the mechanical connection with the accelerator pedal (accelerator operating element) 56 configured in the driver's seat of the vehicle.

[0074] The intake air, regulated by the throttle valve, flows through the intake manifold (not shown) and mixes with the fuel injected from the injector 20 near the intake port of each cylinder to form a gas-fuel mixture. When the intake valve (not shown) is opened, the mixture flows into the combustion chamber (not shown) of the cylinder. The gas-fuel mixture is ignited in the combustion chamber and combusted, driving the piston to rotate the crankshaft 22, and then becoming exhaust gas, which is released to the outside of the engine 10.

[0075] The crankshaft 22 of the engine 10 is connected to the pump impeller 24a of the torque converter 24, while the turbine impeller 24b, which is arranged opposite to it and receives fluid (hydraulic oil), is connected to the main shaft (input shaft) MS. Thus, the rotation of the crankshaft 22 is input to the transmission mechanism 26 via the torque converter 24. The transmission mechanism 26 includes a continuously variable transmission (CVT) 26.

[0076] The CVT 26 includes a main shaft MS, more precisely, a drive wheel 26a disposed on its outer peripheral side shaft, a secondary shaft (output shaft) CS parallel to the main shaft MS, more precisely, a driven wheel 26b disposed on its outer peripheral side shaft, and an annular flexible member, such as a metal belt 26c, surrounding therebetween.

[0077] The driving pulley 26a includes a fixed pulley half 26a1 disposed on the outer peripheral side shaft of the main shaft MS in a manner that prevents relative rotation and movement along the axial direction, and a movable pulley half 26a2 disposed on the outer peripheral side shaft of the main shaft MS in a manner that prevents relative rotation and movement relative to the fixed pulley half 26a1 along the axial direction. The driven pulley 26b includes a fixed pulley half 26b1 disposed on the outer peripheral side shaft of the secondary shaft CS in a manner that prevents relative rotation and movement along the axial direction, and a movable pulley half 26b2 disposed on the secondary shaft CS in a manner that prevents relative rotation and movement relative to the fixed pulley half 26b1 along the axial direction.

[0078] The CVT 26 is connected to the engine 10 via a forward / reverse switching device 28. The forward / reverse switching device 28 includes a forward clutch (disengagement and engagement device) 28a that enables the vehicle to travel in the forward direction, a reverse brake clutch 28b that enables the vehicle to travel in the reverse direction, and a planetary gear mechanism 28c disposed therebetween. The CVT 26 is connected to the engine 10 via the forward clutch 28a.

[0079] In the planetary gear mechanism 28c, the sun gear 28c1 is fixed to the main shaft MS, while the ring gear 28c2 is fixed to the fixed pulley half 26a1 of the driving gear 26a via the forward clutch 28a. A pinion 28c3 is arranged between the sun gear 28c1 and the ring gear 28c2. The pinion 28c3 is connected to the sun gear 28c1 via a gear carrier 28c4. When the reverse brake clutch 28b is engaged, the gear carrier 28c4 is fixed (locked).

[0080] The rotation of the secondary shaft CS is transmitted from the second shaft (intermediate shaft) SS to the drive wheel 12 via gears. That is, the rotation of the secondary shaft CS is transmitted to the second shaft SS via gears 30a and 30b, and the rotation is transmitted from the differential gear 32 via gear 30c to the left and right drive wheels (only the right side is shown) 12.

[0081] In the forward / reverse switching device 28, the switching between the forward clutch 28a and the reverse brake clutch 28b is performed by the driver operating the gear selector 44 located on the driver's seat to select any gear such as P, R, N, or D. The gear selection made by the driver through the gear selector 44 is transmitted to the manual valve of the hydraulic supply mechanism 46 (described below).

[0082] After selecting a gear such as D, S, or L via the gear selector 44, the spool of the manual valve moves accordingly, discharging hydraulic oil (oil pressure) from the piston chamber of the reverse brake clutch 28b. On the other hand, oil pressure is supplied to the piston chamber of the forward clutch 28a, engaging the forward clutch 28a.

[0083] When the forward clutch 28a is engaged, all gears rotate as a unit with the main shaft MS, and the drive wheel 26a is driven in the same direction as the main shaft MS (forward direction), thereby the vehicle travels in the forward direction.

[0084] When the reverse gear (R) is selected, hydraulic oil is discharged from the piston chamber of the forward clutch 28a. Simultaneously, hydraulic pressure is supplied to the piston chamber of the reverse brake clutch 28b, causing the reverse brake clutch 28b to engage. Therefore, the gear carrier 28c4 is fixed, the ring gear 28c2 is driven in the opposite direction to the sun gear 28c1, and the drive wheel 26a is driven in the opposite direction to the main shaft MS (reverse direction), causing the vehicle to travel in the reverse direction.

[0085] After selecting the P or N gear, hydraulic oil is discharged from the piston chamber of both gears, causing the forward clutch 28a and the reverse brake clutch 28b to disengage, disconnecting the power transmission via the forward / reverse switching device 28, thereby blocking the power transmission between the engine 10 and the drive wheel 26a of the CVT 26.

[0086] Figure 2 This is the hydraulic circuit diagram of the hydraulic supply mechanism 46. As shown in the figure, a hydraulic pump 46a is installed in the hydraulic supply mechanism 46. The hydraulic pump 46a includes a gear pump, driven by the engine 10, which draws hydraulic oil stored in the reservoir 46b and pressurizes it to the PH control valve 46c. The output (PH pressure (line pressure)) of the PH control valve 46c is connected from the oil circuit 46d via the first regulating valve 46e and the second regulating valve 46f to the piston chamber (DR) 26a21 of the movable pulley half 26a2 of the drive wheel 26a and the piston chamber (DN) 26b21 of the movable pulley half 26b2 of the driven wheel 26b, and also via the oil circuit 46g to the CR valve 46h.

[0087] CR valve 46h reduces the PH pressure to generate CR pressure (control pressure), which is supplied from oil circuit 46i to the first (electromagnetic) linear solenoid valve 46j, the second (electromagnetic) linear solenoid valve 46k, and the third (electromagnetic) linear solenoid valve 46l.

[0088] The first (electromagnetic) linear solenoid valve 46j and the second linear solenoid valve 46k cause the output pressure determined by the excitation of their solenoids to act on the first regulating valve 46e and the second regulating valve 46f, thereby supplying hydraulic oil at PH pressure delivered from the oil circuit 46d to the piston chambers 26a21 and 26b21 of the movable pulley half 26a2 and the movable pulley half 26b2, respectively, thereby generating pulley side pressure.

[0089] Therefore, pulley side pressure is generated, causing movable pulley halves 26a2 and 26b2 to move along the axial direction. The wheel widths of the driving wheel 26a and driven wheel 26b change, and the winding radius of the belt 26c changes. As described above, by adjusting the pulley side pressure, the ratio (gear ratio) at which the output of the engine 10 is transmitted to the drive wheel 12 can be continuously changed.

[0090] The output (CR pressure) of CR valve 46h is also connected to CR shift valve 46n via oil line 46m, and then connected to piston chamber (FWD) 28a1 of forward clutch 28a and piston chamber (RVS) 28b1 of reverse brake clutch 28b of forward / reverse switching device 28 via manual valve 46o.

[0091] As described above, the manual valve 46o connects the output of the CR shift valve 46n to either the piston chamber 28a1 or the piston chamber 28b1 of the forward clutch 28a and the reverse brake clutch 28b, depending on the position of the gear selector 44 operated (selected) by the driver.

[0092] Furthermore, the output of the PH control valve 46c is sent to the TC regulating valve 46q via the oil circuit 46p, and the output of the TC regulating valve 46q is connected to the LC shift valve 46s via the LC control valve 46r.

[0093] The output of the LC shift valve 46s is connected on one side to the piston chamber 24c1 of the lock-up clutch 24c of the torque converter 24, and on the other side to the chamber 24c2 on its back side.

[0094] Hydraulic oil is supplied to piston chamber 24c1 via LC shift valve 46s. Meanwhile, after being discharged from rear chamber 24c2, lock-up clutch 24c is engaged (opened), and oil is supplied to rear chamber 24c2. Conversely, after being discharged from piston chamber 24c1, lock-up clutch 24c is released (closed). The slippage of lock-up clutch 24c is determined by the amount of hydraulic oil supplied to piston chamber 24c1 and rear chamber 24c2.

[0095] The output of CR valve 46h is connected to LC control valve 46r and LC shift valve 46s via oil circuit 46t, while a fourth linear solenoid valve 46u is inserted in oil circuit 46t. The slippage of lock-up clutch 24c is adjusted (controlled) by the energization / de-energization of the solenoid of the fourth linear solenoid valve 46u.

[0096] return Figure 1 As explained, an engine speed sensor (crank angle sensor) 50 is installed at an appropriate location, such as near the camshaft (not shown) of the engine 10. The engine speed sensor 50 outputs a signal indicating the engine speed NE for each specified crank angle position of the piston.

[0097] A throttle valve opening sensor 54 is provided on the actuator of the DBW mechanism 16. The throttle valve opening sensor 54 outputs a signal proportional to the throttle valve opening TH based on the amount of rotation of the actuator. Furthermore, an accelerator pedal opening sensor 56a is provided near the accelerator pedal 56. The accelerator pedal opening sensor 56a outputs a signal proportional to the accelerator pedal opening AP, which corresponds to the amount of accelerator pedal operation by the driver.

[0098] The outputs of the engine speed sensor 50, etc., are sent to the engine controller (control unit) 66. The engine controller 66 includes a microcomputer that determines the target throttle valve opening based on these sensor outputs, controls the operation of the DBW mechanism 16, and simultaneously determines the fuel injection quantity to drive the injector 20. Furthermore, the engine controller 66 controls the engine speed (idle speed).

[0099] An NT sensor (rotation sensor) 70 is installed on the main spindle MS. The NT sensor 70 outputs a pulse signal indicating the rotational speed of the turbine rotor 24b, specifically the rotational speed NT (transmission input shaft speed) of the main spindle MS, and more specifically the rotational speed of the input shaft of the forward clutch 28a.

[0100] An NDR sensor (rotation sensor) 72 is located near the drive wheel 26a of CVT 26. The NDR sensor 72 outputs a pulse signal corresponding to the rotational speed NDR of the drive wheel 26a, or in other words, the rotational speed of the output shaft of the forward clutch 28a.

[0101] An NDN sensor (rotation sensor) 74 is disposed near the driven wheel 26b. The NDN sensor 74 outputs a pulse signal indicating the rotational speed NDN of the driven wheel 26b, i.e., the rotational speed of the countershaft CS (transmission output shaft rotational speed). A vehicle speed sensor (rotation sensor) 76 is disposed near the gear 30b of the second shaft SS. The vehicle speed sensor 76 outputs a pulse signal indicating the vehicle speed V based on the rotational speed of the second shaft SS.

[0102] A gear selector switch 44a is located near the gear selector 44. The gear selector switch 44a outputs a signal corresponding to the gear selected by the driver, such as R, N, or D.

[0103] like Figure 2 As shown, an oil pressure sensor 82 is installed in the oil passage of the hydraulic supply mechanism 46, which communicates with the driven pulley 26b of the CVT 26. The oil pressure sensor 82 outputs a signal corresponding to the oil pressure supplied to the piston chamber 26b21 of the movable pulley half 26b2 of the driven pulley 26b. Furthermore, an oil temperature sensor 84 is installed in the reservoir 46b. The oil temperature sensor 84 outputs a signal corresponding to the oil temperature (the temperature of the hydraulic oil ATF, TATF). Additionally, as... Figure 2 As shown by the dashed line, the oil pressure sensor 82 can also be configured in the oil passage between the piston chamber 28a1 of the forward clutch 28a and the manual valve 46o, or in the oil passage connected to the lock-up clutch 24c of the torque converter 24, to detect the oil pressure at the aforementioned location.

[0104] The output of NT sensor 70, etc., also includes the output of other sensors not shown, and is transmitted to... Figure 1 The shift controller (control unit) 90 is shown. The shift controller 90 also includes a microcomputer and is configured to communicate freely with the engine controller 66. Based on these detected values, the shift controller 90 energizes / de-energizes the electromagnetic solenoids such as the first opening / closing solenoid 46u and the fourth opening / closing solenoid 46u of the hydraulic supply mechanism 46, thereby controlling the operation of the forward / reverse switching device 28, the CVT 26, and the torque converter 24.

[0105] Next, the transmission control system of CVT 26 will be explained. Figure 3 This is a block diagram representing the CVT transmission control system. The shift controller 90, which controls the transmission ratio of CVT 26, is shown in the figure and includes a target transmission ratio determination unit M1, a transmission ratio feedback proportional-integral-differential (PID) control unit M2, and a transmission ratio feedback gain reduction control execution judgment unit M3.

[0106] The target gear ratio determination unit M1 calculates the target gear ratio of CVT 26 based on the rotational speed of the drive wheel 26a (DR pulley rotational speed) detected by NDR sensor 72, the rotational speed of the driven wheel 26b (DN pulley rotational speed) detected by NDN sensor 74, vehicle speed, accelerator pedal opening, etc. The subtractor 91 calculates the gear ratio deviation by subtracting the actual gear ratio calculated based on the rotational speeds of the drive wheel 26a and driven wheel 26b from the target gear ratio calculated by the target gear ratio determination unit M1. The gear ratio feedback PID control unit M2 performs PID processing on the gear ratio deviation input from the subtractor 91 to calculate the PID feedback control quantity used to converge the deviation to zero. At this time, the gear ratio feedback gain reduction control execution judgment unit M3 executes the gear ratio feedback gain reduction control after making a judgment that it intends to execute the gear ratio feedback gain reduction control, thereby replacing the value of the feedback gain (PID gain). In the gear ratio feedback gain reduction control, specifically, it is determined whether the actual gear ratio is greater than the specified gear ratio. If the actual gear ratio is less than the specified gear ratio, the feedback gain value of the gear ratio in the feedback control is set to a value less than the value when the actual gear ratio is greater than the specified gear ratio. The PID feedback control quantity output from the gear ratio feedback PID control unit M2 is filtered by filter 94 to remove noise components and then provided to the oil pressure supply mechanism 46 as the control value for oil pressure.

[0107] Then, in this embodiment, when the shift controller 90 determines that the NDR sensor (rotation sensor) 72 has malfunctioned or has other defects, it performs a decision on the execution of the shift ratio feedback gain reduction control using the shift ratio feedback gain reduction control execution decision unit M3. Figure 4 This is a time-series graph showing the changes in engine speed (NE), drive wheel speed (NDR), CVT 26 ratio (R), and feedback oil pressure (P) under the conditions of transmission ratio feedback gain reduction control and without transmission ratio feedback gain reduction control. In the graphs showing the changes in values, solid lines represent changes under the condition of no transmission ratio feedback gain reduction control (no control), and dashed lines represent changes under the condition of transmission ratio feedback gain reduction control (with control). Furthermore, single-dotted lines represent the detection value of NDR sensor 72 and the calculated value based on the detection value.

[0108] First, the case where gear ratio feedback gain reduction control is not performed when the NDR sensor 72 malfunctions or suffers a defect (the case of normal gear control using existing methods) will be explained. In this case, at time t1, due to the malfunction of the NDR sensor 72, the detected value of the drive wheel speed (NDR) by the NDR sensor 72 is lower than the actual speed. As a result, the CVT 26 ratio (actual ratio) calculated based on the NDR sensor 72's detection value differs from the target ratio (difference). In order to eliminate the difference between the actual ratio and the target ratio, the feedback oil pressure is increased, and control is performed to shift the CVT 26 to a lower ratio (a larger gear ratio). As a result, the CVT 26 shifts to a lower ratio, causing the engine speed of 10 to increase. Because the NDR sensor 72 malfunctioned, the normal active wheel rotation was not calculated. In this state, the speed was further shifted to the lower ratio, and eventually the speed was continuously shifted to the maximum ratio (lowest ratio: LOW end ratio) that the CVT 26 could mechanically (structurally).

[0109] Next, the case of reducing the gear ratio feedback gain control when the NDR sensor 72 malfunctions (the case of gear control using the method of the present invention) will be described. In this case, at time t1, due to a defect such as a malfunction of the NDR sensor 72, the detected value of the drive wheel rotation number (NDR) detected by the NDR sensor 72 is lower than the actual rotation number. Therefore, the gear ratio feedback gain reduction control execution determination unit M3 determines whether to perform gear ratio feedback gain reduction control. Thus, by reducing the gear ratio feedback gain (the feedback gain value is replaced with a lower value), the gear ratio feedback gain is reduced (the feedback gain value is replaced with a lower value), thereby suppressing the increase in feedback oil pressure and avoiding control that would cause the CVT 26 to shift to an excessively low ratio. Therefore, the actual ratio of the CVT 26 will not increase excessively, thus preventing an excessive increase in the drive wheel rotation number (actual rotation number).

[0110] That is, the smallest ratio that the detection value of NDR sensor 72 can be mechanically (structurally) obtained compared to CVT 26. Figure 4 If the shift ratio (as shown) further shifts towards the OD side (smaller shift ratio), it is determined that the NDR sensor 72 has malfunctioned or is defective, and shifting to an excessively low ratio can be suppressed. Therefore, before a malfunction of the NDR sensor 72 is determined, shifting to an excessively low ratio can be prevented, thus controlling vehicle behavior and ensuring safe movement of the vehicle.

[0111] Here, the execution judgment of the gear ratio feedback gain reduction control using the shift controller 90 is explained. Figure 5This is a graph (gear shift map) illustrating an example of the transmission characteristics of CVT 26. The gear ratio of CVT 26 is calculated from the ratio of the input speed (the speed of the driving wheel 26a) to the output speed (the speed of the driven wheel 26b). In the graph, the horizontal axis represents the vehicle speed V (a parameter corresponding to the output speed of CVT 26). The vertical axis represents the set or target value of the input speed (driving wheel speed NDR) of CVT 26 (hereinafter referred to as "NDR set value"). Furthermore, in the graph, the line L1, representing the slope of the maximum gear ratio, is shown at the low end, and the line L2, representing the slope of the minimum gear ratio, is shown at the overdrive (OD) end. For simplicity, the transmission characteristics related to accelerator opening AP1 to accelerator opening AP4 are shown (furthermore, AP4 > AP3 > AP2 > AP1 are assumed). Furthermore, the line L3 (APOFF) shown as a dashed line in the same graph represents the state where the driver has not operated the accelerator pedal 56 (accelerator is off, that is, the accelerator opening AP detected by the accelerator opening sensor 56a is essentially zero).

[0112] For example, when the accelerator opening AP changes at a certain vehicle speed V (V is set to a constant), the shift controller 90 controls the CVT 26 to change the NDR setting value to a value corresponding to the accelerator opening AP, so that the input speed NDR of the CVT 26 matches the changed NDR setting value (changing the gear ratio). Furthermore, for example, when the vehicle speed V changes at a certain accelerator opening AP (AP is set to a constant), the shift controller 90 controls the CVT 26 to change the NDR setting value to a value corresponding to the vehicle speed V, so that the input speed NDR of the CVT 26 matches the changed NDR setting value.

[0113] In the vehicle's normal driving mode, CVT 26 according to Figure 5 The transmission mapping shown is used for control (changing the transmission ratio of CVT 26 based on the accelerator opening AP and vehicle speed V during driving). For ease of explanation, the diagram here shows the transmission characteristics related to the four accelerator openings AP1 to AP4, but in reality, more transmission characteristics can be prepared in advance or obtained through calculation.

[0114] The gear ratio of CVT 26 continuously varies between the line L1 (LOW end ratio) and the line L2 (OD end ratio) on the graph, and it can operate normally within this range (normal driving mode). Furthermore, the LOW end ratio (line L1) is the maximum ratio that CVT 26 can structurally achieve (mechanically set), and the OD end ratio (line L2) is the minimum ratio that CVT 26 can structurally achieve (mechanically set). Therefore, in the calculated or theoretical values ​​obtained using the shift controller 90, there may be ranges where the CVT 26's ratio is greater than the LOW end ratio (the range on the low speed side or high RPM side of line L1 on the graph) or less than the OD end ratio (the range on the high speed side or low RPM side of line L2 on the graph). However, the ratio that CVT 26 can actually use is the range between the LOW end ratio line L1 and the OD end ratio line L2.

[0115] Furthermore, even if the ratio of CVT 26 is greater than the OD ratio (the area above line L2 in the graph, i.e., the low-speed side or the high-RPM side), from the viewpoint of vehicle stability or safety, the area where the ratio is less than the accelerator opening AP1 (the area below line AP1 in the graph, i.e., the high-speed side and the low-RPM side) is a ratio that is not used for control. That is, the area S1 (the shaded area in the graph) is the range where the target value or the actual value of the ratio obtained by the shift controller 90 is not actually set.

[0116] In addition, Figure 5 In the curve diagram, in the low-speed region below vehicle speed V1, the APOFF line L3 is not aligned with the AP1 line, but rather deviates from the AP1 line towards the lower side. Therefore, in the region below vehicle speed V1, the ratio on the set line L3 (APOFF) becomes a larger ratio than the ratio on AP1 (the lower-side ratio). On the other hand, in the region above vehicle speed V1, the APOFF line L3 aligns with the AP1 line. The region (S1) where the gear ratio is not used in the target gear shift mapping is the region below the gear ratio when the accelerator opening AP is essentially fully closed. The reason for this setting is to shift the ratio towards the lower side in the low-speed region below vehicle speed V1, thereby improving the low-holding performance when the vehicle stops (referring to the performance of preventing the hydraulic circuit from dropping and the ratio from shifting to the higher side when the vehicle stops) or the responsiveness during re-acceleration.

[0117] and, Figure 5The region (S1) of the gear ratio not used in the control of the curve (target gear mapping) is set by the value on the target gear mapping based on the accelerator opening AP and the vehicle speed V when the specified vehicle speed V1 is below and the lock-up clutch 24c of the torque converter 24 is closed.

[0118] Furthermore, in this embodiment, the shift controller 90 implements the gear ratio feedback gain reduction control when either condition 1 or condition 2 is met.

[0119] [Condition 1]

[0120] The shift controller 90 implements shift ratio feedback gain reduction control when the ratio of CVT 26 calculated based on the detection value of NDR sensor 72 is a smaller ratio than the OD end ratio (line L2) (ratio within region S2) (condition 1).

[0121] [Condition 2]

[0122] The shift controller 90 implements shift ratio feedback gain reduction control when the ratio of CVT 26 calculated based on the detection value of NDR sensor 72 is the ratio within region S1 (condition 2). That is, in the region above vehicle speed V1, shift ratio feedback gain reduction control is implemented when the ratio of CVT 26 is below line L3 (APOFF) and accelerator opening AP1; in the region below vehicle speed V1, shift ratio feedback gain reduction control is implemented when the ratio of CVT 26 is below accelerator opening AP1.

[0123] Furthermore, in this embodiment, even if either condition 1 or condition 2 is met, the shift controller 90 does not perform gear ratio feedback gain reduction control when it determines that the road surface on which the vehicle is traveling is a low friction coefficient road (low μ road). The low friction coefficient road determination unit, which determines that the road surface on which the vehicle is traveling is a low friction coefficient road (low μ road), is omitted from illustration and detailed description. For example, it may include a drive force detection unit that detects the drive force of the vehicle's drive wheels 12, a slip rate detection unit that detects the slip rate of the drive wheels 12, and a μ detection unit that detects the μ of the road surface based on the correlation between the drive force and the slip rate of the drive wheels 12. In the low μ road determination process performed using the low friction coefficient road determination unit, for example, a known method as disclosed in Japanese Patent Application Publication No. 8-300964 is used, and the determination is based on whether the vehicle's travel path is a low μ road prone to slippage (low friction coefficient μ).

[0124] As explained above, when the ratio (actual gear ratio) of CVT 26 calculated based on the detection value of NDR sensor 72 is below the specified gear ratio, the shift controller 90 included in this embodiment performs gear ratio feedback gain reduction control, and sets the value of the gear ratio feedback gain in the oil pressure feedback control to be less than the value when the actual gear ratio is greater than the specified gear ratio.

[0125] When the CVT 26 ratio (actual gear ratio) calculated based on the detection value of NDR sensor 72 is below the specified gear ratio, the NDR sensor 72, which detects the rotational speed of the CVT 26's drive pulley 26a, is highly likely to malfunction or suffer from defects. Therefore, by implementing gear ratio feedback gain reduction control, and setting the value of the gear ratio feedback gain in the feedback control to be less than the value when the actual gear ratio is greater than the specified gear ratio, it is possible to prevent the CVT 26 ratio (gear ratio) from shifting to an excessively low (low-speed) ratio, as is the case with existing control methods.

[0126] Furthermore, by utilizing the shift controller 90 of this embodiment, without increasing the number of speed sensors or performing complex control, it is possible to properly determine the fault of the NDR sensor 72, preventing the CVT 26 ratio from shifting to an excessively low ratio. Therefore, it is possible to suppress the increase in vehicle cost, and in the event of an abnormality such as a fault in the NDR sensor 72, it is possible to ensure the stability of the vehicle's behavior until the vehicle stops at a safe location.

[0127] Furthermore, the specified gear ratio can be the gear ratio that the CVT 26 can structurally obtain or a smaller gear ratio. In this embodiment, it is the smallest gear ratio (OD end gear ratio) that the CVT 26 can structurally obtain.

[0128] According to the aforementioned structure, by setting the specified gear ratio to the smallest structurally achievable gear ratio (OD end gear ratio) of CVT 26, the possibility of defects such as NDR sensor 72 malfunctioning is high when the actual gear ratio is below the specified gear ratio. Therefore, by appropriately determining whether NDR sensor 72 is malfunctioning or malfunctioning, and performing gear ratio feedback gain reduction control, the stability of vehicle behavior can be ensured until the vehicle comes to a safe stop.

[0129] Furthermore, in this embodiment, the shift controller 90 has a target shift mapping for obtaining the target shift ratio of the CVT 26. In the region where the target shift ratio (the target shift ratio calculated based on the detection value of the NDR sensor 72) on the target shift mapping is not used in the control, or in the case where it is a shift ratio larger than the smallest shift ratio that the CVT 26 can structurally obtain (region S1), the shift ratio feedback gain reduction control is performed.

[0130] According to the aforementioned structure, the NDR sensor 72 is highly likely to malfunction or experience defects in the region where the target gear ratio on the target gear ratio mapping is not used in control, or in the case of a gear ratio larger than the smallest structurally achievable gear ratio of CVT 26. Therefore, by properly identifying defects such as NDR sensor 72 malfunction and performing gear ratio feedback gain reduction control, the stability of vehicle behavior can be ensured until the vehicle comes to a safe stop.

[0131] Furthermore, in this embodiment, when the specified vehicle speed V1 is above, the region S1 in the target gear shift mapping that is not used in the control is the region below the gear shift ratio (line L3) when the accelerator opening AP is actually in a fully closed (closed) state.

[0132] Furthermore, in this embodiment, the region S1, which is the region of gear ratios that are not used in the target gear mapping, is set by the value of the accelerator opening AP and the vehicle speed V on the target gear mapping when the vehicle speed V is below the specified vehicle speed V1 and the lock-up clutch 24c is closed.

[0133] When the vehicle speed V is below the specified vehicle speed V1, the lock-up clutch 24c of the torque converter 24 is closed. This could potentially cause a temporary change in the drive wheel speed (gear ratio) that serves as the input speed to the CVT 26. Therefore, when the specified vehicle speed V1 is below the specified speed and the lock-up clutch 24c is closed, by setting the gear ratio based on the accelerator opening AP and the vehicle speed V under the state of lock-up clutch 24c being open, the temporary change in the drive wheel speed caused by the lock-up clutch 24c being closed can be ignored, thus enabling proper detection of defects such as a malfunction of the NDR sensor 72.

[0134] Furthermore, in this embodiment, the shift controller 90 does not perform the gear ratio feedback gain reduction control when it determines that the road surface on which the vehicle is traveling is a low friction coefficient road.

[0135] When the vehicle is traveling on a low-friction road surface, there is a possibility of slippage of the drive wheels 12, causing sudden changes in wheel speed, vehicle speed, or acceleration. This could lead to a temporary change in the CVT 26's rotational speed (gear ratio) detected by the NDR sensor 72. Therefore, by not implementing gear ratio feedback gain reduction control when the vehicle is traveling on a low-friction road surface, the temporary changes in CVT 26's rotational speed caused by the low-friction road surface can be ignored, thus allowing for proper identification of defects such as NDR sensor 72 malfunction.

[0136] The embodiments of the present invention have been described above, but the present invention is not limited to the described embodiments. Various modifications can be made within the scope of the claims and the technical concept described in the specification and drawings. For example, in the described embodiment, the rotational speed sensor that is the object of fault diagnosis is shown as an NDR sensor 72 that detects the rotational speed of the drive wheel 26a. Otherwise, the rotational speed sensor that is the object of fault diagnosis in the present invention can also be an NDN sensor 74 that detects the rotational speed of the driven wheel 26b.

Claims

1. A control device for a continuously variable transmission (CVT) for a vehicle, comprising: A continuously variable transmission (CVT) includes: a drive wheel that transmits driving force from a vehicle drive source and rotates; a driven wheel that transmits the driving force associated with the rotation to the output side; and a power transmission member wound between the drive wheel and the driven wheel, which continuously changes the speed of the drive wheel and transmits it to the driven wheel by changing the wheel width of the drive wheel and the driven wheel. A rotation sensor is used to detect the rotational speed of the driving wheel or the driven wheel; A hydraulic supply device supplies hydraulic pressure to the drive wheel; and The control device controls the supply of hydraulic pressure using the hydraulic supply device. The control device for the continuously variable transmission (CVT) for vehicles is characterized in that: The control device performs feedback control of the oil pressure so that the actual gear ratio of the continuously variable transmission (CVT) calculated based on the detection value of the speed sensor becomes the target gear ratio. When the actual gear ratio is below the specified gear ratio, gear ratio feedback gain reduction control is performed, and the value of the gear ratio feedback gain in the feedback control is set to be less than the value when the actual gear ratio is greater than the specified gear ratio. The specified gear ratio is the smallest gear ratio that the continuously variable transmission (CVT) can structurally achieve, or a smaller gear ratio.

2. The control device for a continuously variable transmission (CVT) for vehicles according to claim 1, characterized in that: The control device has a target gear ratio mapping for obtaining the target gear ratio. When the target gear ratio on the target gear ratio map is in the region of gear ratios that are not used in the control and is a gear ratio that is larger than the minimum gear ratio that the continuously variable transmission can structurally obtain, the gear ratio feedback gain reduction control is performed.

3. The control device for a continuously variable transmission (CVT) for vehicles according to claim 2, characterized in that, include: The vehicle speed detection component detects the vehicle speed. The accelerator operating element is operated by the driver of the vehicle; and The accelerator opening detection component detects the accelerator opening caused by the operation of the accelerator operating elements. The region of gear ratios that are not used in the target gear mapping is set based on the accelerator opening and the vehicle speed (V).

4. The control device for a continuously variable transmission (CVT) for vehicles according to claim 3, characterized in that: The region of gear ratios that are not used in the target gear mapping is the region below the gear ratios when the accelerator opening is essentially fully closed.

5. The control device for a continuously variable transmission (CVT) for vehicles according to claim 2, characterized in that, include: A torque converter with a lock-up clutch is mounted on the vehicle. When the vehicle is below a specified speed and the lock-up clutch is closed, the region of gear ratios that are not used in the target gear shift map is set by the value of the accelerator opening and the vehicle speed on the target gear shift map based on the state of the lock-up clutch being open.

6. The control device for a continuously variable transmission (CVT) for vehicles according to claim 1, characterized in that: The specified gear ratio is the smallest gear ratio that can be structurally obtained for a continuously variable transmission (CVT).

7. The control device for a continuously variable transmission (CVT) for vehicles according to claim 2, characterized in that: The specified gear ratio is the smallest gear ratio that can be structurally obtained for a continuously variable transmission (CVT).

8. The control device for a continuously variable transmission (CVT) for vehicles according to claim 1, characterized in that, include: The low-friction coefficient road determination component determines whether the friction coefficient of the road surface on which the vehicle is traveling is below a specified value, thus classifying it as a low-friction coefficient road. When the control device determines that the road surface on which the vehicle is traveling is a low friction coefficient road using the low friction coefficient road determination component, it will not perform the gear ratio feedback gain reduction control.

9. The control device for a continuously variable transmission (CVT) for vehicles according to claim 2, characterized in that, include: The low-friction coefficient road determination component determines whether the friction coefficient of the road surface on which the vehicle is traveling is below a specified value, thus classifying it as a low-friction coefficient road. When the control device determines that the road surface on which the vehicle is traveling is a low friction coefficient road using the low friction coefficient road determination component, it will not perform the gear ratio feedback gain reduction control.

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