JP7461987B2 - Vehicle continuously variable transmission control device - Google Patents

Description

The present invention relates to a control device for a continuously variable transmission for a vehicle, which is configured by wrapping a power transmission member such as a metal chain or belt between a drive pulley and a driven pulley.

A vehicle is configured to change the speed of the output from the drive wheels using a transmission and transmit it to the drive wheels. A well-known example of a transmission is a continuously variable transmission having a belt mechanism in which an endless belt is wound around a drive pulley and a driven pulley with a variable pulley width, as shown in Patent Document 1, for example. This transmission changes the pulley width by controlling the hydraulic pressure of the hydraulic oil supplied to the drive pulley and the driven pulley, and changes the winding radius of the belt around the pulleys, thereby making it possible to change and control the gear ratio steplessly. A vehicle with such a transmission is provided with a control device for controlling the hydraulic pressure according to the vehicle state and for controlling the operation of the transmission.

JP 2022-45709 A

The control device for the continuously variable transmission configured as described above controls the hydraulic pressure supplied to the continuously variable transmission based on the detection value of the rotation speed sensor that detects the rotation speed of the drive pulley and driven pulley of the continuously variable transmission. However, in the unlikely event that the rotation speed sensor is unable to output a normal detection value due to a malfunction such as a breakdown, this may cause problems in the shift control of the continuously variable transmission, so it is necessary to properly determine whether the rotation speed sensor has failed.

Conventionally, a method for determining whether a continuously variable transmission has a fault in its speed sensor has been to detect the difference between the speed of the turbine of a torque converter provided on the input side of the continuously variable transmission and the speed of a rotating element such as a gear provided on the output side, and if the difference is not a normal value, to determine that the speed sensor has failed. However, with this method, it takes a certain amount of time to determine that the speed sensor has failed, and during that time, shift control is performed based on the detection value of the failed speed sensor, which may result in temporary inappropriate control, such as the gear ratio of the continuously variable transmission becoming excessively low.

As another method for determining whether the continuously variable transmission's RPM sensor is faulty, it is possible to control the speed change of the continuously variable transmission using the detection value of another RPM sensor that detects the RPM of rotating elements other than the continuously variable transmission, such as gears or shafts. However, in this case, if a clutch or the like is interposed between the continuously variable transmission and the other rotating elements, and if the engagement state of the clutch is unknown, it is not certain that the detection value of the other RPM sensor accurately reflects the current RPM of the continuously variable transmission, so this method may not be usable.

Furthermore, in case of a malfunction of the RPM sensor, it is possible to provide an additional RPM sensor of a separate system, but doing so may lead to increased costs and weight of the vehicle due to the addition of an RPM sensor.

The present invention has been made to solve the above problems, and its purpose is to provide a control device for a continuously variable transmission that has a relatively simple configuration and control and can maintain appropriate control of the gear ratio of the continuously variable transmission even in the unlikely event that a malfunction such as a failure occurs in the rotation speed sensor of the continuously variable transmission.

In order to solve the above problems, the control device for a continuously variable transmission for a vehicle according to the present invention comprises a drive pulley (26a) which is rotated by the driving force transmitted from the driving source (10) of the vehicle, a driven pulley (26b) which transmits the driving force associated with the rotation to the output side, and a power transmission member (26c) wound between the drive pulley (26a) and the driven pulley (26b), and changes the pulley width of the drive pulley (26a) and the driven pulley (26b) to continuously change the rotation speed of the drive pulley (26a) and transmit it to the driven pulley (26b); A control device for a continuously variable transmission for a vehicle includes a sensor (72), a hydraulic supply device (46) that supplies hydraulic pressure to the drive pulley (26a), and a control device (90) that controls the supply of hydraulic pressure by the hydraulic supply device (46). The control device (90) performs feedback control of the hydraulic pressure so that the actual gear ratio of the continuously variable transmission (26) calculated based on the detection value of the rotation speed sensor (72) becomes a target gear ratio, and performs gear ratio feedback gain reduction control to set the value of the feedback gain of the gear ratio in the feedback control to a smaller value when the actual gear ratio is equal to or smaller than a predetermined gear ratio, compared to when the actual gear ratio is greater than the predetermined gear ratio.

In a control device for a continuously variable transmission for a vehicle, when the actual gear ratio is equal to or lower than a predetermined gear ratio, there is a risk of a malfunction such as a failure in the rotation speed sensor that detects the rotation speed of the drive pulley or driven pulley of the continuously variable transmission. According to the present invention, in such a case, by performing gear ratio feedback gain reduction control that sets the value of the feedback gain of the gear ratio in the feedback control to a smaller value compared to when the actual gear ratio is higher than the predetermined gear ratio, it is possible to prevent the ratio (gear ratio) of the continuously variable transmission from being shifted excessively to the low side (low speed side).

In addition, the control device for a continuously variable transmission for a vehicle according to the present invention can properly determine that a malfunction such as a failure has occurred in the rotation speed sensor without increasing the number of installed rotation speed sensors or performing complex control, and can prevent the ratio (gear ratio) of the continuously variable transmission from being shifted excessively to the low side (low speed side). This makes it possible to prevent an increase in vehicle costs while ensuring the stability of vehicle behavior until the vehicle is stopped in a safe place, even if an abnormality such as a failure occurs in the rotation speed sensor.

In addition, in this control device for a continuously variable transmission for a vehicle, the predetermined gear ratio may be the smallest gear ratio that the continuously variable transmission (26) can structurally have or a gear ratio smaller than that. Note that the smallest gear ratio that the continuously variable transmission can structurally have here may be, as an example, the gear ratio at the OD end of the continuously variable transmission (CVT) in the embodiment described below.

According to this configuration, the predetermined gear ratio is the smallest gear ratio that the continuously variable transmission can structurally attain, and if the actual gear ratio is equal to or less than this predetermined gear ratio, there is a high possibility that a malfunction such as a breakdown has occurred in the rotation speed sensor. Therefore, since it is possible to appropriately determine that a malfunction such as a breakdown has occurred in the rotation speed sensor and perform gear ratio feedback gain reduction control, it is possible to ensure the stability of the vehicle's behavior until the vehicle is stopped in a safe place.

In addition, in this control device for a continuously variable transmission for a vehicle, the control device (90) may have a target gear ratio map for obtaining the target gear ratio, and perform the gear ratio feedback gain reduction control when the target gear ratio on the target gear ratio map is within a range of gear ratios not used for control purposes and is greater than the smallest gear ratio that the continuously variable transmission (26) can structurally have.

According to this configuration, if the target gear ratio on the target shift map is within the range of gear ratios not used for control and is smaller than the smallest gear ratio that the continuously variable transmission can structurally have, there is a high possibility that a malfunction such as a failure has occurred in the rotation speed sensor. Therefore, since it is possible to appropriately determine that a malfunction such as a failure has occurred in the rotation speed sensor and perform gear ratio feedback gain reduction control, it is possible to ensure stability in the behavior of the vehicle until it is stopped in a safe place.

In addition, this control device for a continuously variable transmission for a vehicle includes a vehicle speed detection means (76) for detecting the vehicle speed (V) of the vehicle, an accelerator operator (56) operated by the driver of the vehicle, and an accelerator opening detection means (56a) for detecting the accelerator opening (AP) caused by the operation of the accelerator operator (56), and the region (S1, S2) of the gear ratio that is not used for control in the target shift map may be set based on the accelerator opening (AP) and the vehicle speed (V).

In addition, the region (S1, S2) of the gear ratio that is not used for control in the target shift map may be a region equal to or lower than the gear ratio when the accelerator opening (AP) is substantially fully closed.

In addition, this control device for a continuously variable transmission for a vehicle may include a torque converter (24) with a lock-up clutch (24c) mounted on the vehicle, and when the vehicle speed is equal to or lower than a predetermined vehicle speed (V1) and the lock-up clutch (24c) is off, the region (S1) of the gear ratio that is not used for control in the target shift map may be set to a value on the target shift map based on the accelerator opening (AP) and the vehicle speed (V) when the lock-up clutch (24c) is on.

When the vehicle speed is below a predetermined speed, the lock-up clutch of the torque converter mounted on the vehicle is turned off, which may cause a temporary change in the drive pulley rotation speed, which is the input rotation speed of the continuously variable transmission (gear ratio). Therefore, when the vehicle speed is below the predetermined speed and the lock-up clutch is turned off, a region of the gear ratio that is not used for control is set in the target shift map based on the accelerator opening and vehicle speed when the lock-up clutch is on. This makes it possible to properly determine whether a malfunction such as a failure has occurred in the rotation speed sensor without being affected by the temporary change in the drive pulley rotation speed caused by the lock-up clutch of the torque converter being turned off.

The control device for the vehicle continuously variable transmission may further include a low friction coefficient road determination means for determining whether the friction coefficient of the road surface on which the vehicle is traveling is a low friction coefficient road that is equal to or less than a predetermined value, and the control device (90) may not perform the gear ratio feedback gain reduction control when the low friction coefficient road determination means determines that the road surface on which the vehicle is traveling is a low friction coefficient road.

When the road surface on which the vehicle is traveling is a low friction coefficient road, abrupt fluctuations may occur in the wheel speed or vehicle speed and their acceleration values due to wheel slippage, etc., which may cause a temporary change in the rotation speed (gear ratio) of the continuously variable transmission detected by the rotation speed sensor. Therefore, by not performing the gear ratio feedback gain reduction control when the road surface on which the vehicle is traveling is a low friction coefficient road, it is possible to appropriately determine that a malfunction such as a failure of the rotation speed sensor has occurred without being affected by the temporary change in the rotation speed of the continuously variable transmission caused by the road surface on which the vehicle is traveling being a low friction coefficient road.
The reference numerals in parentheses above are examples of the reference numerals of components in the embodiment described below.

The control device for a continuously variable transmission for a vehicle according to the present invention has a relatively simple configuration and control, and can maintain proper control of the gear ratio of the continuously variable transmission even in the unlikely event that a malfunction such as a failure occurs in the rotation speed sensor of the continuously variable transmission.

1 is a schematic diagram showing an example of the overall configuration of a vehicle equipped with a control device for a vehicle continuously variable transmission according to an embodiment of the present invention; FIG. 4 is a hydraulic circuit diagram of a hydraulic supply mechanism. 2 is a block diagram showing a shift control system of a CVT (continuously variable transmission). 6 is a timing chart showing the change over time of each value when the gear ratio feedback gain reduction control is not performed and when it is performed; FIG. 4 is a diagram showing a target gear ratio map for obtaining a target value of the gear ratio.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 1 is a schematic diagram showing an example of the overall configuration of a vehicle equipped with a control device for a continuously variable transmission for a vehicle according to one embodiment of the present invention. The vehicle shown in the figure is equipped with an automatic transmission 1 including an engine (internal combustion engine) 10 as a drive source, a torque converter 24 with a lock-up clutch 24c, a speed change mechanism (continuously variable transmission mechanism) 26 that changes the speed of rotation caused by the driving force of the engine 10 and outputs it, and a forward/reverse switching device 28. The forward/reverse switching device 28 includes a forward clutch 28a provided to connect and disconnect the transmission of the driving force of the engine 10 to the speed change mechanism 26. The vehicle also includes an engine controller 66 and a shift controller 90, which are control devices for controlling the engine 10, the speed change mechanism 26, and the forward/reverse switching device 28.

The throttle valve (not shown) located in the intake system of the engine 10 is connected to a DBW (Drive By Wire) mechanism 16 consisting of an actuator such as an electric motor that is mechanically disconnected from an accelerator pedal (accelerator operator) 56 located at the driver's seat of the vehicle, and is opened and closed by the DBW mechanism 16.

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

The crankshaft 22 of the engine 10 is connected to a pump impeller 24a of a torque converter 24, while a turbine runner 24b, which faces the pump impeller 24a and receives a fluid (hydraulic oil), is connected to a main shaft (input shaft) MS. As a result, the rotation of the crankshaft 22 is input to a transmission mechanism 26 via the torque converter 24. The transmission mechanism 26 is made up of a Continuous Variable Transmission (hereafter referred to as "CVT") 26.

The CVT 26 is made up of a main shaft MS, more precisely a drive pulley 26a arranged on the outer circumferential shaft, a counter shaft (output shaft) CS parallel to the main shaft MS, more precisely a driven pulley 26b arranged on the outer circumferential shaft, and an endless flexible member, such as a metal belt 26c, wound between them.

The drive pulley 26a is composed of a fixed pulley half 26a1 arranged on the outer circumferential shaft of the main shaft MS, which is non-rotatable and non-movable in the axial direction, and a movable pulley half 26a2, which is non-rotatable and non-movable in the axial direction relative to the fixed pulley half 26a1 on the outer circumferential shaft of the main shaft MS. The driven pulley 26b is composed of a fixed pulley half 26b1 arranged on the outer circumferential shaft of the counter shaft CS, which is non-rotatable and non-movable in the axial direction, and a movable pulley half 26b2, which is non-rotatable and non-movable in the axial direction relative to the fixed pulley half 26b1 on the outer circumferential shaft of the counter shaft CS.

The CVT 26 is connected to the engine 10 via a forward/reverse switching device 28. The forward/reverse switching device 28 is composed of a forward clutch (disconnecting device) 28a that allows the vehicle to travel in the forward direction, a reverse brake clutch 28b that allows the vehicle to travel in the reverse direction, and a planetary gear mechanism 28c disposed between them. The CVT 26 is connected to the engine 10 via the forward clutch 28a.

In the planetary gear mechanism 28c, the sun gear 28c1 is fixed to the main shaft MS, and the ring gear 28c2 is fixed to the fixed pulley half 26a1 of the drive pulley 26a via the forward clutch 28a. A pinion 28c3 is disposed between the sun gear 28c1 and the ring gear 28c2. The pinion 28c3 is connected to the sun gear 28c1 by a carrier 28c4. When the reverse brake clutch 28b is operated, the carrier 28c4 is fixed (locked) thereby.

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

In the forward/reverse switching device 28, the forward clutch 28a and the reverse brake clutch 28b are switched by the driver operating a range selector 44 provided at the driver's seat to select one of the ranges, such as P, R, N, or D. The range selection made by the driver operating the range selector 44 is transmitted to a manual valve in the hydraulic supply mechanism 46 (described later).

When the D, S, or L range is selected via the range selector 44, the spool of the manual valve moves accordingly, and hydraulic oil (hydraulic pressure) is discharged from the piston chamber of the reverse brake clutch 28b, while hydraulic pressure is supplied to the piston chamber of the forward clutch 28a, engaging the forward clutch 28a.

When the forward clutch 28a is engaged, all gears rotate together with the main shaft MS, and the drive pulley 26a is driven in the same direction as the main shaft MS (forward direction), so that the vehicle travels in the forward direction.

When the R range is selected, hydraulic oil is discharged from the piston chamber of the forward clutch 28a, while hydraulic pressure is supplied to the piston chamber of the reverse brake clutch 28b, activating the reverse brake clutch 28b. As a result, the carrier 28c4 is fixed, the ring gear 28c2 is driven in the opposite direction to the sun gear 28c1, the drive pulley 26a is driven in the opposite direction to the main shaft MS (reverse direction), and the vehicle travels in reverse.

When the P or N range is selected, hydraulic oil is discharged from both piston chambers, the forward clutch 28a and the reverse brake clutch 28b are both released, power transmission through the forward/reverse switching device 28 is cut off, and power transmission between the engine 10 and the drive pulley 26a of the CVT 26 is interrupted.

Figure 2 is a hydraulic circuit diagram of the hydraulic supply mechanism 46. As shown in the figure, the hydraulic supply mechanism 46 is provided with a hydraulic pump 46a. The hydraulic pump 46a is a gear pump driven by the engine 10, and pumps up the hydraulic oil stored in the reservoir 46b and pumps it to the PH control valve 46c. The output (PH pressure (line pressure)) of the PH control valve 46c is connected on the one hand from the oil passage 46d via the first and second regulator valves 46e and 46f to the piston chamber (DR) 26a21 of the movable pulley half 26a2 of the drive pulley 26a of the CVT 26 and the piston chamber (DN) 26b21 of the movable pulley half 26b2 of the driven pulley 26b, and on the other hand to the CR valve 46h via the oil passage 46g.

The CR valve 46h reduces the PH pressure to generate CR pressure (control pressure) and supplies it from the oil passage 46i to the first, second, and third (electromagnetic) linear solenoid valves 46j, 46k, and 46l. The first and second linear solenoid valves 46j and 46k act on the first and second regulator valves 46e and 46f with output pressures determined according to the excitation of their solenoids, thereby supplying hydraulic oil at PH pressure sent from the oil passage 46d to the piston chambers 26a21 and 26b21 of the movable pulley halves 26a2 and 26b2, generating pulley side pressure accordingly.

As a result, pulley lateral pressure is generated that moves the movable pulley halves 26a2 and 26b2 in the axial direction, changing the pulley width of the drive pulley 26a and the driven pulley 26b, and changing the winding radius of the belt 26c. In this way, by adjusting the pulley lateral pressure, the ratio (gear ratio) that transmits the output of the engine 10 to the drive wheels 12 can be changed continuously.

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

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

In addition, the output of the PH control valve 46c is sent to the TC regulator valve 46q via the oil passage 46p, and the output of the TC regulator valve 46q is connected to the LC shift valve 46s via the LC control valve 46r.

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

When hydraulic oil is supplied to the piston chamber 24c1 through the LC shift valve 46s and discharged from the rear chamber 24c2, the lock-up clutch 24c is engaged (ON), and when hydraulic oil is supplied to the rear chamber 24c2 and discharged from the piston chamber 24c1, the lock-up clutch 24c is released (OFF). The amount of slip of the lock-up clutch 24c is determined by the amount of hydraulic oil supplied to the piston chamber 24c1 and the rear chamber 24c2.

The output of the CR valve 46h is connected to the LC control valve 46r and the LC shift valve 46s via an oil passage 46t, and a fourth linear solenoid valve 46u is inserted in the oil passage 46t. The amount of slip of the lock-up clutch 24c is adjusted (controlled) by energizing and de-energizing the solenoid of the fourth linear solenoid valve 46u.

Returning to the explanation of FIG. 1, an engine speed sensor (crank angle sensor) 50 is provided at an appropriate position, 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 predetermined crank angle position of the piston.

The actuator of the DBW mechanism 16 is provided with a throttle opening sensor 54. The throttle opening sensor 54 outputs a signal proportional to the throttle valve opening TH through the amount of rotation of the actuator. In addition, an accelerator opening sensor 56a is provided near the accelerator pedal 56. The accelerator opening sensor 56a outputs a signal proportional to the accelerator opening AP, which corresponds to the amount of accelerator pedal operation by the driver.

The outputs of the engine speed sensor 50 and other sensors are sent to an engine controller (control means) 66. The engine controller 66 is equipped with a microcomputer, and determines the target throttle opening based on the sensor outputs to control the operation of the DBW mechanism 16, and determines the fuel injection amount to drive the injector 20. The engine controller 66 also controls the engine speed (idle speed).

The main shaft MS is provided with an NT sensor (revolutions per minute sensor) 70. The NT sensor 70 outputs a pulse signal indicating the rotation speed of the turbine runner 24b, specifically the rotation speed NT (transmission input shaft rotation speed) of the main shaft MS, more specifically the input shaft rotation speed of the forward clutch 28a.

An NDR sensor (revolutions per minute sensor) 72 is provided near the drive pulley 26a of the CVT 26. The NDR sensor 72 outputs a pulse signal corresponding to the revolutions per minute NDR of the drive pulley 26a, in other words, the output shaft revolutions per minute of the forward clutch 28a.

An NDN sensor (rpm sensor) 74 is provided near the driven pulley 26b. The NDN sensor 74 outputs a pulse signal indicating the rpm NDN of the driven pulley 26b, i.e., the rpm of the countershaft CS (transmission output shaft rpm). A vehicle speed sensor (rpm sensor) 76 is provided near the gear 30b of the secondary shaft SS. The vehicle speed sensor 76 outputs a pulse signal indicating the vehicle speed V through the rpm of the secondary shaft SS.

A range selector switch 44a is provided near the range selector 44. The range selector switch 44a outputs a signal corresponding to the range selected by the driver, such as R, N, or D.

As shown in FIG. 2, an oil pressure sensor 82 is disposed in the oil passage leading to the driven pulley 26b of the CVT 26 in the oil pressure supply mechanism 46. 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. An oil temperature sensor 84 is disposed in the reservoir 46b. The oil temperature sensor 84 outputs a signal corresponding to the oil temperature (temperature TATF of the hydraulic oil ATF). The oil pressure sensor 82 may be disposed in the oil passage between the piston chamber 28a1 of the forward clutch 28a and the manual valve 46o, or in the oil passage leading to the lock-up clutch 24c of the torque converter 24, as shown by imaginary lines in FIG. 2, to detect the oil pressure at that location.

The outputs of the NT sensor 70 and other sensors, including those of other sensors not shown, are sent to a shift controller (control means) 90 shown in FIG. 1. The shift controller 90 also includes a microcomputer and is configured to communicate freely with the engine controller 66. Based on these detection values, the shift controller 90 excites and de-excites electromagnetic solenoids such as the first and fourth on/off solenoids 46u of the hydraulic supply mechanism 46 to control the operation of the forward/reverse switching device 28, the CVT 26, and the torque converter 24.

Next, the shift control system of the CVT 26 will be described. FIG. 3 is a block diagram showing the CVT shift control system. As shown in the figure, the shift controller 90 that controls the gear ratio of the CVT 26 includes a target gear ratio determination unit M1, a gear ratio feedback PID control unit M2, and a gear ratio feedback gain reduction control execution determination unit M3.

The target gear ratio determination unit M1 calculates the target gear ratio of the CVT 26 based on the rotation speed (DR pulley rotation speed) of the drive pulley 26a detected by the NDR sensor 72, the rotation speed (DN pulley rotation speed) of the driven pulley 26b detected by the NDN sensor 74, the vehicle speed, the accelerator pedal opening, etc. The subtractor 91 calculates the deviation of the gear ratio by subtracting the actual gear ratio calculated based on the rotation speed of the drive pulley 26a and the rotation speed of the driven pulley 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 deviation of the gear ratio input from the subtractor 91 and calculates a PID feedback control amount for converging the deviation to zero. At that time, the gear ratio feedback gain reduction control execution determination unit M3 executes the gear ratio feedback gain reduction control when it is determined that the gear ratio feedback gain reduction control should be executed, thereby changing the value of the feedback gain (PID gain). Specifically, in the gear ratio feedback gain reduction control, it is determined whether the actual gear ratio is greater than a predetermined gear ratio, and if the actual gear ratio is smaller than the predetermined gear ratio, the feedback gain value of the gear ratio in the feedback control is set to a smaller value than when the actual gear ratio is greater than the predetermined gear ratio. The PID feedback control amount output from the gear ratio feedback PID control unit M2 has noise components removed by a filter 94, and is provided to the hydraulic pressure supply mechanism 46 as a hydraulic pressure control value.

In this embodiment, when the shift controller 90 determines that the NDR sensor (rpm sensor) 72 has a malfunction such as a failure, the execution determination unit M3 of the gear ratio feedback gain reduction control determines whether to execute the gear ratio feedback gain reduction control. FIG. 4 is a timing chart showing the changes in the engine speed (NE), drive pulley speed (NDR), CVT 26 ratio (R), and feedback hydraulic pressure (P) when the gear ratio feedback gain reduction control is executed and when it is not executed. In the changes in each value shown in the graph in the figure, the change in the value when the gear ratio feedback gain reduction control is not executed (no control) is shown by a solid line, and the change in the value when the gear ratio feedback gain reduction control is executed (with control) is shown by a dotted line. In addition, the detection value of the NDR sensor 72 and the calculation value based on the detection value are shown by a dashed line.

First, a case where gear ratio feedback gain reduction control is not performed when a malfunction such as a failure occurs in the NDR sensor 72 (when normal gear shift control by a conventional method is performed) will be described. In this case, when a malfunction such as a failure occurs in the NDR sensor 72 at time t1, the detection value of the drive pulley rotation speed (NDR) detected by the NDR sensor 72 becomes lower than the actual rotation speed, and a difference (difference) occurs between the ratio (actual ratio) of the CVT 26 calculated based on the detection value of the NDR sensor 72 and the target ratio. Then, in order to fill the difference between the actual ratio and the target ratio, the feedback hydraulic pressure is increased and control is performed to shift the ratio of the CVT 26 to a lower ratio (larger gear ratio). As a result, the ratio of the CVT 26 is shifted to the lower ratio, and the rotation speed of the engine 10 increases. Because the NDR sensor 72 is broken, the normal drive pulley rotation speed cannot be calculated, and the gear shift to the lower ratio continues, and finally the gear shift continues until the CVT 26 reaches the maximum ratio that it is mechanically (structurally) capable of achieving (the lowest ratio: LOW end ratio).

Next, a case where the gear ratio feedback gain reduction control is performed when the NDR sensor 72 is broken (a case where the gear shift control according to the method of the present invention is performed) will be described. In this case, a malfunction such as a malfunction occurs in the NDR sensor 72 at time t1, causing the detection value of the drive pulley rotation speed (NDR) detected by the NDR sensor 72 to be lower than the actual rotation speed, and the gear ratio feedback gain reduction control execution judgment unit M3 judges that the gear ratio feedback gain reduction control is to be performed. As a result, the gear ratio feedback gain is reduced by the gear ratio feedback gain reduction control (the feedback gain value is switched to a lower value), suppressing an increase in feedback hydraulic pressure and preventing the control of shifting the ratio of the CVT 26 to an excessively low ratio. As a result, the actual ratio of the CVT 26 does not increase excessively, and therefore an excessive increase in the drive pulley rotation speed (actual rotation speed) can be prevented.

In other words, if the detection value of the NDR sensor 72 transitions to a further OD side (smaller gear ratio) than the minimum ratio that the CVT 26 can mechanically (structurally) assume (the OD end ratio shown in FIG. 4), it is determined that the NDR sensor 72 has a malfunction or other problem, and shifting to an excessively low ratio is suppressed. This makes it possible to prevent shifting to an excessively low ratio until a malfunction of the NDR sensor 72 is confirmed, making it possible to control the vehicle behavior so that the vehicle can be driven safely during that time.

Here, the execution judgment of the gear ratio feedback gain reduction control by the shift controller 90 will be described. FIG. 5 is a graph (gear shift map) showing an example of the gear shift characteristics of the CVT 26. The gear ratio of the CVT 26 is given by the ratio of the input rotation speed (the rotation speed of the drive pulley 26a) to the output rotation speed (the rotation speed of the driven pulley 26b). In the graph of the figure, the horizontal axis indicates the vehicle speed V (a parameter corresponding to the output rotation speed of the CVT 26). Also, the vertical axis indicates the set value or target value (hereinafter simply referred to as the "NDR set value") of the input rotation speed (drive pulley rotation speed NDR) of the CVT 26. Also, in this graph, a line L1 at the low (LOW) end is shown as a slope indicating the maximum gear ratio, and a line L2 at the overdrive (OD) end is shown as a slope indicating the minimum gear ratio. For ease of explanation, the shift characteristics for accelerator openings AP1 to AP4 are shown here (where AP4>AP3>AP2>AP1). Also, the dotted line L3 (APOFF) in the graph in the figure is the line when the driver is not operating the accelerator pedal 56 (accelerator off, i.e., the accelerator opening AP detected by the accelerator opening sensor 56a is essentially zero).

For example, if the accelerator opening AP changes at a certain vehicle speed V (with the accelerator opening AP held constant), the shift controller 90 changes the NDR setting value to a value corresponding to the accelerator opening AP, and controls the CVT 26 (changing the gear ratio) so that the input speed NDR of the CVT 26 follows the changed NDR setting value. Also, for example, if the vehicle speed V changes at a certain accelerator opening AP (with the accelerator opening AP held constant), the shift controller 90 changes the NDR setting value to a value corresponding to the vehicle speed V, and controls the CVT 26 so that the input speed NDR of the CVT 26 follows the changed NDR setting value.

In the vehicle's normal driving mode, the CVT 26 is controlled according to the shift map shown in FIG. 5 (the gear ratio of the CVT 26 is changed based on the accelerator opening AP and the vehicle speed V while driving). For ease of explanation, shift characteristics for four accelerator openings AP1 to AP4 are shown here, but in reality, many more shift characteristics may be prepared in advance or obtained by calculation.

The ratio (gear ratio) of the CVT 26 changes continuously between the LOW end ratio line L1 and the OD end ratio line L2 in the graph, and normal operation (normal driving mode) can be performed within this range. The LOW end ratio (line L1) here is the maximum ratio that the CVT 26 can have structurally (that can be mechanically set), and the OD end ratio (line L2) is the minimum ratio that the CVT 26 can have structurally (that can be mechanically set). Therefore, the calculated values or theoretical values by the shift controller 90 may result in a range in which the ratio of the CVT 26 is greater than the LOW end ratio (a range on the lower vehicle speed or higher rotation speed side than line L1 in the graph) or a range in which the ratio is smaller than the OD end ratio (a range on the higher vehicle speed or lower rotation speed side than line L2 in the graph), but the ratio that can actually be used with the CVT 26 is the range between line L1 of the LOW end ratio and line L2 of the OD end ratio.

In addition, even if the CVT 26 ratio is in a range (above line L2 in the graph, i.e., the low vehicle speed or high RPM area) that is larger than the OD end ratio, the range (below line AP1 in the graph, i.e., the high vehicle speed and low RPM area) that is smaller than the accelerator opening AP1 line is a ratio range that is not used for control purposes from the standpoint of vehicle behavior stability and safety. In other words, this range S1 (shaded area in the graph) is a range that is not actually set as the target ratio value or actual ratio value by the shift controller 90.

In the graph of FIG. 5, in the low vehicle speed range below vehicle speed V1, the APOFF line L3 does not coincide with the AP1 line and deviates from the AP1 line to the low side, so that in the range below vehicle speed V1, the ratio on line L3 (APOFF) is set to be a larger ratio (lower ratio) than the ratio on AP1. On the other hand, in the range above vehicle speed V1, the APOFF line L3 coincides with the AP1 line, and the range (S1) of the gear ratio that is not used for control in the target shift map is the range below the gear ratio when the accelerator opening AP is substantially in a fully closed state. The reason for this setting is that by shifting the ratio to the lower side in the low vehicle speed range below vehicle speed V1, the low holding performance when the vehicle is stopped (meaning the performance that can prevent the hydraulic pressure of the hydraulic circuit from decreasing and the ratio from shifting to the high side when the vehicle is stopped) and the responsiveness when accelerating again are improved.

In addition, in the graph of FIG. 5 (target shift map), the region (S1) of the gear ratio that is not used for control purposes is set to a value on the target shift map based on the accelerator opening AP and vehicle speed V when the lock-up clutch 24c is on when the vehicle speed is below a predetermined vehicle speed V1 and the lock-up clutch 24c of the torque converter 24 is off.

In this embodiment, the shift controller 90 performs the above-mentioned gear ratio feedback gain reduction control when either condition 1 or condition 2 below is met.

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

[Condition 2]
The shift controller 90 performs the gear ratio feedback gain reduction control when the ratio of the CVT 26 calculated based on the detection value of the NDR sensor 72 is within region S1 (condition 2). That is, in the region where the vehicle speed is V1 or more, the gear ratio feedback gain reduction control is performed when the ratio of the CVT 26 is equal to or less than line L3 (APOFF) and accelerator opening AP1, and in the region where the vehicle speed is V1 or less, the gear ratio feedback gain reduction control is performed when the ratio of the CVT 26 is equal to or less than accelerator opening AP1.

In this embodiment, even if either condition 1 or condition 2 is met, the shift controller 90 does not perform the gear ratio feedback gain reduction control if it is determined 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 that determines that the road surface on which the vehicle is traveling is a low friction coefficient road (low μ road) is not shown and is not described in detail, but can be composed of, for example, a driving force detection unit that detects the driving force of the driving wheels 12 of the vehicle, a slip ratio detection unit that detects the slip ratio of the driving wheels 12, and a μ detection unit that detects the μ of the road surface based on the correlation between the driving force of the driving wheels 12 and the slip ratio. In the low μ road determination process by this low friction coefficient road determination unit, a known method such as that shown in JP Patent Publication No. 8-300964 is used to determine whether the road on which the vehicle is traveling is a slippery (low friction coefficient μ) low μ road.

As described above, when the ratio (actual gear ratio) of the CVT 26 calculated based on the detection value of the NDR sensor 72 is equal to or less than a predetermined gear ratio, the shift controller 90 provided in the vehicle of this embodiment performs gear ratio feedback gain reduction control to set the value of the gear ratio feedback gain in the hydraulic feedback control to a smaller value compared to when the actual gear ratio is greater than the predetermined gear ratio.

When the ratio (actual gear ratio) of the CVT 26 calculated based on the detection value of the NDR sensor 72 is equal to or lower than a predetermined gear ratio, there is a high possibility that the NDR sensor 72, which detects the rotation speed of the drive pulley 26a of the CVT 26, has a malfunction such as a breakdown. Therefore, by performing gear ratio feedback gain reduction control that sets the value of the feedback gain of the gear ratio in the feedback control to a smaller value compared to when the actual gear ratio is higher than the predetermined gear ratio, it is possible to prevent the ratio (gear ratio) of the CVT 26 from being shifted excessively to the low side (low speed side) ratio as in conventional control.

In addition, the control by the shift controller 90 of this embodiment can appropriately determine a failure of the NDR sensor 72 and prevent the ratio (gear ratio) of the CVT 26 from being excessively shifted to the low side (low speed side) ratio without increasing the number of installed rotation speed sensors or performing complex control. This makes it possible to ensure stability of vehicle behavior until the vehicle is stopped in a safe place in the event of an abnormality such as a failure of the NDR sensor 72 while suppressing an increase in vehicle costs.

The above-mentioned specified gear ratio may be a gear ratio that the CVT 26 can structurally assume or a smaller gear ratio, and in this embodiment, it is the smallest gear ratio (OD end gear ratio) that the CVT 26 can structurally assume.

According to this configuration, the predetermined gear ratio is the smallest gear ratio (OD end gear ratio) that the CVT 26 can structurally attain, and if the actual gear ratio is equal to or less than this predetermined gear ratio, there is a high possibility that a malfunction such as a breakdown has occurred in the NDR sensor 72. Therefore, since it is possible to appropriately determine that a malfunction such as a breakdown has occurred in the NDR sensor 72 and perform gear ratio feedback gain reduction control, it is possible to ensure stability in the behavior of the vehicle until the vehicle is stopped in a safe place.

In addition, in this embodiment, the shift controller 90 has a target gear ratio map for obtaining the target gear ratio of the CVT 26, and performs the above-mentioned gear ratio feedback gain reduction control when the target gear ratio on this target gear ratio map (the target gear ratio calculated based on the detection value of the NDR sensor 72) is within a region of gear ratios not used for control, or is a gear ratio greater than the smallest gear ratio that the CVT 26 can structurally have (region S1).

According to this configuration, if the target gear ratio on the target shift map is within the range of gear ratios not used for control, or is a gear ratio greater than the smallest gear ratio that the CVT 26 can structurally have, there is a high possibility that a malfunction such as a failure has occurred in the NDR sensor 72. Therefore, since it is possible to appropriately determine that a malfunction such as a failure has occurred in the NDR sensor 72 and perform gear ratio feedback gain reduction control, it is possible to ensure stability in the behavior of the vehicle until the vehicle is stopped in a safe place.

In addition, in this embodiment, when the vehicle speed is equal to or greater than a predetermined vehicle speed V1, the region S1, which is the region of the gear ratio that is not used for control in the target shift map, is the region below the gear ratio (line L3) when the accelerator opening AP is substantially fully closed (OFF).

In addition, in this embodiment, the region S1, which is the region of the gear ratio that is not used for control in the target shift map, is set to a value on the target shift map based on the accelerator opening AP and vehicle speed V when the lockup clutch 24c is on when the vehicle speed is below a predetermined vehicle speed V1 and the lockup clutch 24c is off.

When the vehicle speed V is below a predetermined vehicle speed V1, the lock-up clutch 24c of the torque converter 24 mounted on the vehicle is turned off, which may cause a temporary change in the drive pulley rotation speed, which is the input rotation speed of the CVT 26 (gear ratio). Therefore, when the vehicle speed is below the predetermined vehicle speed V1 and the lock-up clutch 24c is turned off, a shift map is set based on the accelerator opening AP and the vehicle speed V when the lock-up clutch 24c is on, so that it is possible to properly determine whether a malfunction such as a failure has occurred in the NDR sensor 72 without being affected by the temporary change in the drive pulley rotation speed caused by the lock-up clutch 24c of the torque converter 24 being turned off.

In addition, in this embodiment, if it is determined that the road surface on which the vehicle is traveling is a low friction coefficient road, the shift controller 90 does not perform the above-mentioned gear ratio feedback gain reduction control.

When the road surface on which the vehicle is traveling is a low friction coefficient road, a sudden change in the wheel speed or vehicle speed and their acceleration may occur due to slippage of the drive wheels 12, which may cause a temporary change in the rotation speed (gear ratio) of the CVT 26 detected by the NDR sensor 72. Therefore, by not performing gear ratio feedback gain reduction control when the road surface on which the vehicle is traveling is a low friction coefficient road, it is possible to appropriately determine that a malfunction such as a failure has occurred in the NDR sensor 72 without being affected by a temporary change in the rotation speed of the CVT 26 caused by the road surface on which the vehicle is traveling being a low friction coefficient road.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. For example, in the above embodiment, the rotation speed sensor subject to failure judgment is the NDR sensor 72 that detects the rotation speed of the drive pulley 26a, but in addition to this, the rotation speed sensor subject to failure judgment in the present invention may also be the NDN sensor 74 that detects the rotation speed of the driven pulley 26b.

REFERENCE SIGNS LIST 1 Automatic transmission 10 Engine 12 Drive wheels 16 DBW mechanism 20 Injector 22 Crankshaft 24 Torque converter 24a Pump impeller 24b Turbine runner 24c Lock-up clutch 26 Transmission mechanism (CVT)
26a: drive pulley 26b: driven pulley 26c: belt (power transmission member)
28 Forward/reverse switching device 32 Differential 44 Range selector 44a Range selector switch 46 Hydraulic pressure supply mechanism 50 Engine speed sensor 54 Throttle opening sensor 56 Accelerator pedal 56a Accelerator opening sensor 66 Engine controller 70 NT sensor (speed sensor)
72 NDR sensor (rotation speed sensor)
74 NDN sensor (revolution sensor)
76 Vehicle speed sensor 82 Oil pressure sensor 84 Oil temperature sensor 90 Shift controller MS Main shaft CS Counter shaft SS Secondary shaft M1 Target gear ratio determination unit M2 Gear ratio feedback PID control unit M3 Gear ratio feedback gain reduction control execution determination unit

Claims (11)

a continuously variable transmission including a drive pulley that is rotated by a driving force transmitted from a driving source of a vehicle, a driven pulley that transmits the driving force associated with the rotation to an output side, and a power transmission member wound between the drive pulley and the driven pulley, and which changes the pulley widths of the drive pulley and the driven pulley to continuously change the rotation speed of the drive pulley and transmit the rotation speed to the driven pulley;
a rotation speed sensor for detecting a rotation speed of either the drive pulley or the driven pulley;
A hydraulic pressure supply device that supplies hydraulic pressure to the drive pulley;
A control device for a vehicle continuously variable transmission comprising: a control device for controlling the supply of hydraulic pressure by the hydraulic pressure supply device,
The control device includes:
feedback control of the hydraulic pressure so that an actual speed ratio of the continuously variable transmission calculated based on a detection value of the rotation speed sensor becomes a target speed ratio;
a control device for a continuously variable transmission for a vehicle, characterized in that, when the actual speed ratio is equal to or less than a predetermined speed ratio which is the smallest speed ratio that the continuously variable transmission can structurally attain or is smaller than the smallest speed ratio, a speed ratio feedback gain reduction control is performed in which a value of a feedback gain of the speed ratio in the feedback control is set to a smaller value compared to when the actual speed ratio is larger than the predetermined speed ratio. The control device includes:
a target gear ratio map for obtaining the target gear ratio,
2. The control device for a continuously variable transmission for a vehicle according to claim 1, wherein the gear ratio feedback gain reduction control is performed when the target gear ratio on the target gear map is within a region of gear ratios not used for control and is a gear ratio that is greater than the smallest gear ratio that the continuously variable transmission can structurally have . a continuously variable transmission including a drive pulley that is rotated by a driving force transmitted from a driving source of a vehicle, a driven pulley that transmits the driving force associated with the rotation to an output side, and a power transmission member wound between the drive pulley and the driven pulley, and which changes the pulley widths of the drive pulley and the driven pulley to continuously change the rotation speed of the drive pulley and transmit the rotation speed to the driven pulley;
a rotation speed sensor for detecting a rotation speed of the drive pulley or the driven pulley;
a vehicle speed detection means for detecting a vehicle speed of the vehicle;
an accelerator operator operated by a driver of the vehicle;
an accelerator opening detection means for detecting an accelerator opening caused by operation of the accelerator operator;
A hydraulic pressure supply device that supplies hydraulic pressure to the drive pulley;
A control device that controls the supply of hydraulic pressure by the hydraulic pressure supply device;
A control device for a vehicle continuously variable transmission comprising:
The control device includes:
A target gear ratio map is provided for obtaining a target gear ratio.
feedback control of the hydraulic pressure so that an actual speed ratio of the continuously variable transmission calculated based on a detection value of the rotation speed sensor becomes the target speed ratio;
a control device for a vehicle continuously variable transmission, characterized in that when the actual gear ratio is equal to or lower than a predetermined gear ratio, and when the target gear ratio on the target gear map is within a region of gear ratios not used for control that is set based on the accelerator opening and the vehicle speed and is a gear ratio that is higher than a smallest gear ratio that the continuously variable transmission can structurally have, a gear ratio feedback gain reduction control is performed to set a value of a gear ratio feedback gain in the feedback control to a smaller value compared to when the actual gear ratio is higher than the predetermined gear ratio. a vehicle speed detection means for detecting a vehicle speed of the vehicle, an accelerator operation element operated by a driver of the vehicle, and an accelerator opening detection means for detecting an accelerator opening degree caused by operation of the accelerator operation element,
3. The control device for a continuously variable transmission for a vehicle according to claim 2 , wherein a region of the gear ratio that is not used for control in the target shift map is set based on the accelerator opening and the vehicle speed. 5. The control device for a vehicle continuously variable transmission according to claim 3, wherein a region of the gear ratio not used for control in the target shift map is a region equal to or lower than the gear ratio when the accelerator opening is substantially in a fully closed state. A torque converter with a lock-up clutch is mounted on the vehicle,
5. The control device for a continuously variable transmission for a vehicle according to claim 3 or 4, characterized in that, when the vehicle is at or below a predetermined vehicle speed and the lock-up clutch is off, a region of the target shift map of gear ratios that is not used for control is set by a value on the target shift map that is based on the accelerator opening and the vehicle speed when the lock-up clutch is on. 2. The control device for a vehicle continuously variable transmission according to claim 1 , wherein the predetermined speed ratio is the smallest speed ratio that the continuously variable transmission can structurally have. a low-friction coefficient road determination means for determining whether or not a friction coefficient of a road surface on which the vehicle is traveling is a low-friction coefficient road having a friction coefficient equal to or less than a predetermined value;
2. The control device for a continuously variable transmission for a vehicle according to claim 1, characterized in that the control device does not perform the gear ratio feedback gain reduction control when the low friction coefficient road determination means determines that the road surface on which the vehicle is traveling is a low friction coefficient road. a continuously variable transmission including a drive pulley that is rotated by a driving force transmitted from a driving source of a vehicle, a driven pulley that transmits the driving force associated with the rotation to an output side, and a power transmission member wound between the drive pulley and the driven pulley, and which changes the pulley widths of the drive pulley and the driven pulley to continuously change the rotation speed of the drive pulley and transmit the rotation speed to the driven pulley;
a rotation speed sensor for detecting a rotation speed of the drive pulley or the driven pulley;
A hydraulic pressure supply device that supplies hydraulic pressure to the drive pulley;
A control device that controls the supply of hydraulic pressure by the hydraulic pressure supply device;
a low-friction coefficient road determination means for determining whether or not a road surface on which the vehicle is traveling is a low-friction coefficient road having a friction coefficient equal to or less than a predetermined value ;
A control device for a vehicle continuously variable transmission comprising:
The control device includes:
A target gear ratio map is provided for obtaining a target gear ratio.
feedback control of the hydraulic pressure so that an actual speed ratio of the continuously variable transmission calculated based on a detection value of the rotation speed sensor becomes the target speed ratio;
performing a gear ratio feedback gain reduction control for setting a value of a feedback gain of the gear ratio in the feedback control to a smaller value in a case where the actual gear ratio is equal to or smaller than a predetermined gear ratio and in a case where the target gear ratio on the target gear map is within a region of gear ratios not used in control and is larger than the smallest gear ratio that the continuously variable transmission can structurally assume, compared to a case where the actual gear ratio is larger than the predetermined gear ratio;
a control device for a continuously variable transmission for a vehicle, characterized in that when the low friction coefficient road determination means determines that the road surface on which the vehicle is traveling is a low friction coefficient road, the control device does not perform the gear ratio feedback gain reduction control. The control device for a continuously variable transmission for a vehicle according to any one of claims 1 to 4 and 7 to 9, characterized in that the predetermined gear ratio is a gear ratio at which there is a high possibility that a malfunction is occurring in the rotation sensor. The gear ratio feedback gain reduction control is executed when the vehicle is traveling in a forward direction.
10. The control device for a vehicle continuously variable transmission according to claim 1, wherein the control device is a step of controlling a step of changing a speed of the vehicle.

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