TRANSMISSION CONTROL METHOD

Abstract

A transmission control method for a vehicle, comprising: determining a target transmission ratio from the rotational speed of a transmission input shaft (22) to the rotational speed of a transmission output shaft (24) in response to a signal in a first state, independent of any accelerator pedal position and dependent on a vehicle speed and a drive axle torque request when the axle torque request is valid, and determining the target transmission ratio in response to a signal in a second state based on the vehicle speed and an accelerator pedal position when the axle torque is not valid;controlling the opening of a first valve based on the desired gear ratio, wherein the first valve controls a transmission fluid flow to a first pulley actuator (34) and wherein the first pulley actuator (34) is connected to the transmission input shaft (22) of a continuously variable transmission (CVT) (14) and expands and contracts based on a first pressure of the transmission fluid applied to the first pulley actuator (34);and controlling the opening of a second valve based on the desired gear ratio, wherein the second valve controls a transmission fluid flow to the second pulley actuator (36), and wherein the second pulley actuator (36) is connected to the transmission output shaft (24) of the CVT (14) and expands and contracts based on a second pressure of the transmission fluid applied to the second pulley actuator (36), and wherein one of (i) a belt (38) and (ii) a chain (38) surrounds the first and second pulley actuators (34, 36).

Description

TECHNICAL AREA The present invention relates to transmission control methods for vehicles. Known vehicle systems and associated control methods can be found, for example, in documents DE 11 2011 105 942 T5, DE 41 12 413 A1 and US 2011 / 0 238 272 A1. BACKGROUND An internal combustion engine burns an air-fuel mixture in cylinders to drive the pistons and generate engine torque. Airflow in the engine can be regulated by a throttle. More precisely, the throttle sets the throttle range, which increases or decreases the airflow in the engine. As the throttle range increases, so does the airflow in the engine. A fuel control system adjusts the amount of fuel injected to deliver a desired air / fuel mixture to the cylinders and / or to achieve a desired output torque. Increased air and fuel supply to the cylinders increases the engine's output torque. Some transmission control systems control multiple solenoid valves to shift gears in an automatic transmission. In one example, the transmission control system actuates (e.g., opens) one or more solenoid valves to shift the transmission into a specific gear. The transmission control system actuates a solenoid valve by adjusting the pressure in a line that supplies hydraulic fluid to the solenoid valve. In another example, the transmission control system increases the hydraulic pressure supplied to a solenoid valve to actuate the solenoid valve. Manual transmissions require a driver to operate a clutch pedal and select a gear ratio using a gear selector. The number of gear ratios available to the driver in a manual transmission can range from five to seven, although a greater or lesser number is possible. A continuously variable transmission (CVT) is an automatic transmission that can continuously adjust its gear ratio across a wide range of ratios between maximum and minimum values. SUMMARY According to the invention, a transmission control method for a vehicle is presented, which is characterized by the features of claim 1. Furthermore, a transmission control system for a vehicle is described. A target ratio module determines a target ratio of the transmission input shaft speed to the transmission output shaft speed in response to a signal in a first state, independent of the accelerator pedal position and dependent on the vehicle speed and a torque request from the drive axle. A first pulley valve control module controls the opening of a first valve based on the target ratio. The first valve controls the transmission fluid flow to the first pulley actuator. The first pulley actuator is connected to the transmission input shaft of a continuously variable transmission (CVT) and expands and contracts based on a first pressure of the transmission fluid applied to the first pulley actuator.A second pulley valve control module controls the opening of a second valve based on the desired gear ratio. This second valve controls the transmission fluid flow with a second pulley actuator. The second pulley actuator is connected to the CVT's transmission output shaft and expands and contracts based on a second pressure of the transmission fluid applied to the second pulley actuator. A (i) belt and a (ii) chain surround the first and second pulley actuators. In further features, the target transmission module, in response to the signal in the first state, determines the target transmission depending on the vehicle speed and the torque request of the drive axle using a lookup table that links vehicle speeds and torque requests of the drive axle to achieve target transmission ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. In further features, the target transmission module selects the lookup table, based on a vehicle drive mode, from several lookup tables for respective drive modes, with each of the lookup tables combining the vehicle speeds and torque requests of the drive axle to achieve target transmission ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. In further features, the target transmission module, in response to the signal to a second state, determines the target transmission independently of the torque request of the drive axle and depending on the vehicle speed and the accelerator pedal position. In further features, the target gear ratio module, in response to the signal in the second state, determines the target gear ratio depending on the vehicle speed and the accelerator pedal position using a second lookup table that links vehicle speeds and accelerator pedal positions to target gear ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. In further features, the target transmission module selects the second lookup table, based on a vehicle drive mode, from several second lookup tables for respective drive modes, with each of the second lookup tables combining the vehicle speeds and accelerator pedal positions to achieve target transmission ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. In further features, the target gear ratio module determines the target gear ratio depending on the vehicle speed and the torque request of the drive axle in response to the stipulations that for both: the signal is in the first state; and a configuration display stored in memory indicates that the vehicle is configured to determine the target gear ratio depending on the vehicle speed and the torque request of the drive axle. In further features, the target gear ratio module determines the target gear ratio independently of the torque request of the drive axle and depending on the vehicle speed and the accelerator pedal position in response to a determination that the configuration display indicates that the vehicle is not configured to determine the target gear ratio depending on the vehicle speed and the torque request of the drive axle. In further features, the target transmission module determines the target transmission ratio depending on the vehicle speed and the torque request of the drive axle in response to the signal that remains in the first state for longer than a predetermined period. Further features of the transmission control method include, in response to the signal in the first state, the determination of the target transmission ratio as a function of the vehicle speed and the torque request of the drive axle using a lookup table that links vehicle speeds and torque requests of the drive axle to target transmission ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. Further features of the transmission control method, based on a vehicle drive mode, include selecting the lookup table from several lookup tables for respective drive modes, with each of the lookup tables linking the vehicle speeds and drive axle torque requests to target ratios of the transmission input shaft speed to the transmission output shaft speed. In further features, the transmission control method includes, in response to the signal in a second state, the determination of the target gear ratio independently of the torque request of the drive axle and depending on the vehicle speed and the accelerator pedal position. Further features of the transmission control method include, in response to the signal in the second state, the determination of the target gear ratio as a function of the vehicle speed and the accelerator pedal position using a second lookup table that links vehicle speeds and accelerator pedal positions to target gear ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. In further features, the transmission control method, based on a vehicle drive mode, includes selecting the second lookup table from several second lookup tables for respective drive modes, with each of the second lookup tables linking the vehicle speeds and accelerator pedal positions to target ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. Further features of the transmission control method include determining the target gear ratio depending on the vehicle speed and the torque request of the drive axle in response to the determination that for both: the signal is in the first state; and a configuration display stored in memory indicates that the vehicle is configured to determine the target gear ratio depending on the vehicle speed and the torque request of the drive axle. Further features of the transmission control method include determining the target gear ratio independently of the torque request from the drive axle and depending on the vehicle speed and accelerator pedal position in response to a determination that the configuration display indicates that the vehicle is not configured to determine the target gear ratio depending on the vehicle speed and the torque request from the drive axle. Further features of the transmission control method include the determination of the target gear ratio depending on the vehicle speed and the torque request of the drive axle, in response to the signal that remains in the first state for longer than a predetermined period. Further applications of the present invention will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more readily understood with the aid of the detailed description and the accompanying drawings, wherein: Figs. 1A-1B show a functional block diagram of an exemplary vehicle system; Fig. 2 is a functional block diagram of an exemplary continuously variable transmission (CVT) system; Fig. 3 is a functional block diagram of an exemplary transmission fluid control system; Fig. 4 is a functional block diagram of an exemplary engine control system; Fig. 5 is a flowchart with an exemplary method for controlling a transmission ratio of the speed of the transmission input shaft to the speed of the transmission output shaft of a transmission. The same reference numbers are used in the drawings for similar and / or identical elements. DETAILED DESCRIPTION Some vehicles may include an internal combustion engine and / or one or more electric motors or motor-generator units. Output torque from an engine and / or one or more electric motors is transmitted to a drive system via a transmission. The transmission may be a continuously variable transmission (CVT). According to the present invention, a control module, such as a transmission control module, controls the transmission based on a target gear ratio from the speed of the transmission input shaft to the speed of the transmission output shaft. The control module determines the target gear ratio based on vehicle speed and an axle torque request, if the axle torque request is valid. If the axle torque is not valid, the control module determines the target gear ratio based on vehicle speed and accelerator pedal position. Figures 1A and 1B show functional block diagrams of an exemplary vehicle system. An internal combustion engine 12 drives a transmission 14 via a torque converter 16. The engine 12 can be, for example, a gasoline engine, a diesel engine, or another suitable engine type. A vehicle can also include one or more electric motors and / or motor generator units (MGUs), such as MGU 18. The motor 12 transmits torque to the torque converter 16 via a motor output shaft 20, such as a crankshaft. The torque converter 16 delivers torque to the transmission 14 via a transmission input shaft 22. The electric motor(s) and / or MGU(s) can also transmit torque to the transmission input shaft 22 to supplement or replace motor torque output. An MGU can, under certain circumstances, convert mechanical energy into electrical energy, for example, to recharge one or more batteries and / or to power electronic components of the vehicle. The transmission 14 transmits torque between the transmission input shaft 22 and a transmission output shaft 24. The drive ratio can refer to or be based on the ratio between the rotational speed of the transmission input shaft 22 and the rotational speed of the transmission output shaft 24. The transmission output shaft 24 drives a drive system 26, and the drive system 26 transmits torque to the wheels (not shown) of the vehicle. A range selector knob 28 allows a user to select an operating mode for the transmission 14. The mode can include, for example, a park mode, a reverse mode, a neutral mode, or one or more forward drive modes. The transmission 14 is a continuously variable transmission (CVT). A primary pulley 30 is connected to and rotates with the transmission input shaft 22. A secondary pulley 32 is connected to and rotates with the transmission output shaft 24. The primary pulley 30 includes a primary pulley actuator 34, which expands and contracts based on the pressure of the transmission fluid applied to the primary pulley actuator 34. The secondary pulley 32 includes a secondary pulley actuator 36, which expands and contracts based on the pressure of the transmission fluid applied to the secondary pulley actuator 36. As shown in Fig. 1B, a belt or chain 38 surrounds the primary and secondary pulleys 30 and 32 to rotate the transmission input shaft 22 and the transmission output shaft 24. The extension and contraction of the primary and secondary pulley actuators 34 and 36 vary the rotational ratio between the transmission input shaft 22 and the transmission output shaft 24. The engine control module (ECM) 60 controls the operation of a motor 12. The ECM 60, or another control module (not shown), can control the operation of one or more electric motors and / or MGUs in various applications. A transmission control module (TCM) 70 controls the operation of the transmission 14. While the TCM 70 is shown implemented inside the transmission 14, it can also be implemented outside the transmission 14 in various applications. The ECM 60 and TCM 70 can share data. With reference to Fig. 2, a functional block diagram of an exemplary use of the CVT system is presented. The CVT 14 comprises a transmission fluid pump 104, which draws transmission fluid from a reservoir 112 or another suitable transmission fluid source. The transmission fluid pump 104 is mechanically driven by the engine 12, for example by rotation of the crankshaft 20 or the transmission input shaft 22. The transmission fluid pump 104 transfers the transmission fluid to a pressure regulating valve 116 via a first fluid path. The transmission fluid pump 104 also transfers the transmission fluid to a switching valve 120 via a second fluid path. When the switching valve 120 is open, the transmission fluid flows from the transmission fluid pump 104 through the switching valve 120 to the pressure regulating valve 116. In various applications, the switching valve 120 can be integrated within the transmission fluid pump 104. The pressure control valve 116 regulates the transmission fluid flow to a primary pulley valve 124, a secondary pulley valve 128, and / or to one or more other actuators / functions 132. The other actuators and / or functions 132 may include, for example, the torque converter 16 (e.g., clutch), one or more variable solenoid blow-off valves (VBS) that regulate the transmission fluid flow to the reservoir 112, cool the CVT 14, and / or lubricate the components of the CVT 14. An output pressure of the pressure control valve 116 can be described as line pressure 122. The primary pulley valve 124 regulates the flow (and pressure) of the transmission fluid to the primary pulley actuator 34. For example, the primary pulley valve 124 can be opened to increase the transmission fluid flow to the primary pulley actuator 34 and expand the primary pulley actuator 34. The primary pulley valve 124 can be closed to decrease the transmission fluid flow to the primary pulley actuator 34 and contract the primary pulley actuator 34. An output pressure of the primary pulley valve 124 can be described as the primary pulley pressure 126. The secondary pulley valve 128 regulates the flow (and pressure) of the transmission fluid to the secondary pulley actuator 36. For example, the secondary pulley valve 128 can be opened to increase the transmission fluid flow at the secondary pulley actuator 36, thus expanding the secondary pulley actuator 36. Conversely, the secondary pulley valve 128 can be closed to decrease the transmission fluid flow at the secondary pulley actuator 36, thus contracting the secondary pulley actuator 36. The output pressure of the secondary pulley valve 128 can be described as the secondary pulley pressure 136. Corresponding VBS valves (not shown) can, for example, regulate the transmission fluid flow from the primary and secondary pulley actuators 34 and 36 back to the reservoir 112. A fluid control module 150 controls the actuator of the switching valve 120, the pressure regulating valve 116, the primary pulley valve 124, and the secondary pulley valve 128. Generally, the fluid control module 150 actuates the switching valve 120 at one of two discrete positions at any given time: an open position or a closed position. The fluid control module 150 transfers the switching valve 120 between these two discrete positions under certain circumstances. When the switching valve 120 is in the closed position, the transmission fluid pump 104 operates in partial mode (e.g., half-power). In the closed position, the switching valve 120 blocks the transmission fluid flow in the second fluid path, so the transmission fluid pump 104 pumps transmission fluid only through the first fluid path to the pressure regulating valve 116. Since the transmission fluid pump 104 is driven by the motor 12, an increase in fuel efficiency (i.e., a reduction in fuel consumption) of the motor 12 (compared to full-mode operation) can be achieved during partial mode operation as the transmission fluid pump 104, resulting in a lower torque load on the motor 12. In some applications, the switching valve 120 can be omitted, and the transmission fluid pump 104 pumps transmission fluid only through the first fluid path to the pressure regulating valve 116. When the switching valve 120 is in the open position, the transmission fluid pump 104 operates in full mode. The switching valve 120 activates the transmission fluid flow of the second fluid path in the open position, so that the transmission fluid pump 104 pumps transmission fluid through the first and second fluid paths to the pressure control valve 116. The fluid control module 150 can transfer the switching valve 120 from the closed to the open position under various circumstances. For example, only the fluid control module 150 can transfer the switching valve 120 from the closed to the open position if the change in the target ratio between the input and output shafts 22 and 24 is greater than a predetermined value. With reference to Fig. 3, a functional block diagram of an exemplary transmission fluid control system is shown. The fluid control module 150 can be implemented independently within the transmission control module (TCM) 70 or within other suitable modules. A target ratio module 204 determines a target ratio 208 (between the input and output shafts 22 and 24) which is achieved using the primary and secondary pulley actuators 34 and 36. As discussed below, the target ratio module 204 determines the target ratio 208 based on either: an accelerator pedal position (APP) 212 and a vehicle speed 216 (and independently of a torque request from the drive axle 218); or the torque request from the drive axle 218 and the vehicle speed 216 (and independently of the accelerator pedal position 212). A target pressure module 220 determines a primary pulley target pressure 224 and a secondary pulley target pressure 228 based on the target ratio 208. The primary pulley target pressure 224 corresponds to a target value of the primary pulley pressure 126. The secondary pulley target pressure 228 corresponds to a target value of the secondary pulley pressure 136. The target pressure module 220 can determine the primary pulley pressure 224 and the secondary pulley pressure 228, for example, using one or more lookup tables or functions that relate the target ratio 208 to the primary pulley target pressure 224 and the secondary pulley target pressure 228. A primary valve control module 232 controls the opening of the primary pulley valve 124 based on the primary pulley setpoint pressure 224. The primary valve control module 232 can, for example, control the opening of the primary pulley valve 124 in a closed-loop control system based on the difference between the primary pulley setpoint pressure 224 and a measured or estimated value of the primary pulley pressure 126. Thus, for example, the primary valve control module 232 can open the primary pulley valve 124 while the primary pulley setpoint pressure 224 increases and may even reverse. A secondary valve control module 236 controls the opening of the secondary pulley valve 128 based on the secondary pulley setpoint pressure 228. The secondary valve control module 236 can, for example, control the opening of the secondary pulley valve 128 in a closed-loop control system based on the difference between the secondary pulley setpoint pressure 228 and a measured or estimated value of the secondary pulley pressure 136. Thus, the secondary valve control module 236 can, for example, open the secondary pulley valve 128 while the secondary pulley setpoint pressure 228 increases and may even reverse. The fluid control module 150 can also control the actuator of the pressure regulating valve 116, the actuator of the switching valve 120, the transmission fluid pump 104, and / or one or more other actuators of a transmission. Fig. 4 includes a functional block diagram of an exemplary engine control system. The ECM 60 includes a drive torque module 304, which determines a drive torque request 308 based on driver inputs 312. The driver input 312 may include, for example, the accelerator pedal position 212, a brake pedal position (BPP), and / or cruise control input. The drive torque module 304 determines the drive torque request 308 based on one or more lookup tables that link the driver inputs to the drive torque request. Drive torque request 308 is an axle torque request. Axle torques (including axle torque requests) refer to torque at the wheels. As discussed below, drive torques (including propulsion torque requests) differ from axle torques in that drive torques refer to torque at the crankshaft. The axle torque arbitration module 316 arbitrates between the drive torque request 308 and other axle torque requests 320. Axle torque (torque at the wheels) can be generated by various sources, including the motor 12 and / or one or more MGUs, such as MGU 18. Examples of the other axle torque requests 320 include a torque reduction request by a traction control system when positive wheel slip is detected, a torque increase request to counteract negative wheel slip, brake management requests to reduce axle torque to ensure that the axle torque does not exceed the braking capacity to stop the vehicle when the vehicle is stopped, and vehicle overspeed torque requests to reduce axle torque to prevent the vehicle from exceeding a predetermined speed.The axle torque arbitration module 316 transmits one or more axle torque requests 324 based on the results of the arbitration between the received axle torque requests 308 and 320. The hybrid control module 328 can determine how much torque should be generated by the motor 12 and how much torque should be produced by the MGU(s). The hybrid control module 328 transmits one or more torque requests 332 to a drive torque arbitrator module 336. The torque requests 332 specify how much torque should be generated by the motor 12. While the hybrid control module 328 is shown as implemented within the ECM 60, it can also be implemented outside the ECM 60 in various hybrid vehicle systems. The hybrid control module 328 can be omitted in non-hybrid vehicles. The drive torque arbitration module 336 converts the torque requests 332 from an axle torque range (torque at the wheels) into a drive torque range (torque at the crankshaft). The drive torque arbitration module 336 arbitrates the converted torque requests with other drive torque requests 340. Examples of the other drive torque requests 340 include torque reductions requested to protect against motor overspeed and torque increases requested to protect against stalling. The drive torque arbitration module 336 transmits one or more drive torque requests 344 to an actuator control module 348 as a result of the arbitration. The actuator control module 348 controls one or more actuators 352 of the engine 12, based on the drive torque requests 344. For example, the actuator control module 348 can, based on the drive torque requests 344, control the opening of a throttle valve, the timing of the ignition of the spark plugs, the timing and quantity of fuel by the injectors, cylinder actuation / deactivation devices, the intake and exhaust valves, one or more boost devices (e.g. turbocharger, supercharger, etc.), an exhaust gas recirculation (EGR) valve and / or one or more other engine actuators. Referring to Fig. 3, the fluid control module 150 also includes a selection module 370. The selection module 370 determines whether the torque request of the drive axis 218 is valid. For example, only the torque request of the drive axis 218 should be the drive torque request 308. The torque request from drive axle 218 is received by the ECM 60 via a Car Area Network (CAN) bus (not shown). The ECM 60 transmits a validity signal with (or within) the torque request from drive axle 218. The ECM 60 sets the validity signal to indicate that the torque request from drive axle 218 is valid if the ECM 60 has correctly determined the torque request from drive axle 218, no fault has been diagnosed in one or more components (e.g., APP sensor, BPP sensors, lookup table, etc.) used to determine the torque request from drive axle 218, and / or one or more other conditions for a valid torque request from drive axle 218 are met. The ECM 60 sets the validity signal to indicate that the torque request from drive axle 218 is invalid if one or more conditions for a valid torque request from drive axle 218 are not met. Selection module 370 determines whether the torque request of drive axle 218 is valid, based on the validity signal. For example, selection module 370 determines that the torque request of drive axle 218 is valid if the validity signal indicates that the torque request of drive axle 218 is valid. Selection module 370 determines that the torque request of drive axle 218 is invalid if the validity signal indicates that the torque request of drive axle 218 is invalid. Selection module 370 also determines whether the vehicle is calibrated to enable the determination of the target gear ratio 208 based on the torque request from the drive axle. For example, selection module 370 can determine whether a calibration indicator stored in memory shows that the vehicle is being calibrated to determine the target gear ratio 208 based on torque requests from the drive axle. The calibration indicator can be stored, for example, by the vehicle manufacturer before the vehicle is made available for driving. The selection module 370 generates a selection signal 374 based on whether (i) the torque request from the drive axle 218 is valid and (ii) the vehicle is calibrated to allow the determination of the target gear ratio 208 based on the torque request from the drive axle. For example, the selection module 370 can set the selection signal 374 to a first state if the torque request from the drive axle 218 is valid and the vehicle is calibrated to allow the determination of the target gear ratio 208 based on the torque request from the drive axle. The selection module 370 can set the selection signal 374 to a second state if at least: (i) a torque request from the drive axle 218 is invalid; and (ii) the vehicle is not calibrated to allow the determination of the target gear ratio 208 based on the torque request from the drive axle.If the selection signal 374 is in the second state and the vehicle is calibrated to allow the determination of the target gear ratio 208 based on the drive axle torque request, the selection module 370 can transfer the selection signal 374 to the first state if the drive axle torque request 218 is valid for at least a predetermined time period. This avoids frequent switching of the selection signal 374 from the second state to the first state. The fluid control module 150 is transferred by the transition from using the drive axle torque request 218 to using the accelerator pedal position 212 in a manner consistent with the configured control strategy of the fluid control module 150. If a step change is permitted, a step change from one gear ratio to another can be commanded. Otherwise, a continuous gear ratio change can be commanded.One example strategy that allows step changes is a tap mode, where a driver commands step changes (shifting up and down). Based on the selection signal 374, the target gear ratio module 204 selects either: the accelerator pedal position 212 and the vehicle speed 216; or the torque request of the drive axle 218 and the vehicle speed 216. For example, the target gear ratio module 204 selects the torque request of the drive axle 218 and the vehicle speed 216 when the selection signal 374 is in the first state. The target gear ratio module 204 selects the accelerator pedal position 212 and the vehicle speed 216 when the selection signal 374 is in the second state. When the selection signal 374 is in the first state, the target gear ratio module 204 determines the target gear ratio 208 based on the torque request of the drive axle 218 and the vehicle speed 216, using a first lookup table 378 stored in memory. The first lookup table 378 can be a three-dimensional representation that links the drive axle torque request and vehicle speeds with the target gear ratios. When the selection signal 374 is in the second state, the target gear ratio module 204 determines the target gear ratio 208 based on the accelerator pedal position 212 and the vehicle speed 216, using a second lookup table 382 stored in memory. The second lookup table 382 can be a three-dimensional representation that links the accelerator pedal positions and vehicle speeds with the target gear ratios.The target translation module 204 can use interpolation for values ​​between entries of the first or second lookup tables 378 or 382. In various applications, multiple examples from the first lookup table 378 can be stored for different driving conditions, such as Normal, Sawtooth, Deceleration, Tap, Operation, Sport, and / or Winter. Multiple examples from the second lookup table 382 can also be stored for the different driving modes. The target gear ratio module 204 can select one of the examples from the chosen lookup tables based on the driving mode. Referring to Fig. 5, a flowchart illustrating an example procedure for controlling the transmission 14 is shown. The control can begin at step 404, where the selection module 370 determines whether the controller area network (CAN) communication of the torque request from the drive axle 218 was successful. If step 404 is correct, the control can determine a gear ratio based on a predetermined axle torque at step 408, and the control proceeds to step 432, which is discussed below. If step 404 is incorrect, the control proceeds to step 412. At 412, the selection module 370 determines whether the torque request from drive axis 218 is valid. For example, the selection module 370 can determine whether the validity signal indicates that the torque request from drive axis 218 is valid. If 412 is correct, the controller proceeds to 416. If 412 is incorrect, the selection module 370 sets the selection signal 374 to the second state and sets a timer at 418, and the controller proceeds to 428, which is discussed below. Selection module 370 determines whether the vehicle is calibrated to enable the determination of the target gear ratio 208 based on torque requests from the drive axle at 416. For example, selection module 370 can determine whether a calibration indicator stored in memory shows that the vehicle is being calibrated to determine the target gear ratio 208 based on torque requests from the drive axle. If 416 is correct, the control unit proceeds to 420. If 416 is incorrect, selection module 370 sets selection signal 374 to the second state and sets the timer at 418, and the control unit proceeds to 428.The timer measures a period of time since the target gear ratio 208 began to be determined based on the accelerator pedal position 212 and the vehicle speed 216 by at least one of the following: vehicles that are not calibrated to allow the determination of the target gear ratio 208 based on the drive axle torque request; and the drive axle torque request 218, which is impermissible. At 420, the selection module 370 can determine whether the measured timer period is longer than a predefined period. If 420 is false, the selection module 370 allows the timer to continue incrementing, sets the selection signal 374 to the second state, and the controller proceeds to 428. If 420 is true, the selection module 370 sets the selection signal 374 to the first state, and the controller proceeds to 424. Comparing the timer periods with the predefined periods can prevent frequent transitions from using the accelerator pedal position 212 and the vehicle speed 216 to using the drive axle torque request 218 and the vehicle speed 216. At 424, the target gear ratio module 204, based on the selection signal 374 in the first state, determines the target gear ratio 208 based on the torque request of the drive axle 218 and the vehicle speed 216 using the first lookup table 378. The target gear ratio module 204 can also select an example from the first lookup table 378 at 424 based on the driving mode. As described above, the first lookup table 378 maps torque requests of the drive axle and vehicle speeds to the target gear ratios. At 428, the target gear ratio module 204, based on the selection signal 374 in the second state, determines the target gear ratio 208 based on the accelerator pedal position 212 and the vehicle speed 216 using the second lookup table 382. The target gear ratio module 204 can also select an example from the second lookup table 382 at 428 based on the driving mode. As described above, the second lookup table 382 maps accelerator pedal positions and vehicle speeds to the target gear ratios. The control system proceeds with 432 to 408, 424, or 428. At 432, the transmission actuators are controlled to achieve the target gear ratio 208 of the speed of the transmission input shaft to the speed of the transmission output shaft. For example, the target pressure module 220 can determine the primary pulley target pressure 224 and the secondary pulley target pressure 228 based on the target gear ratio 208. The primary valve control module 232 can control the opening of the primary pulley valve 124 based on the primary pulley target pressure 224. The secondary valve control module 236 can control the opening of the secondary pulley valve 128 based on the secondary pulley target pressure 228. While Fig. 5 is shown as ending after 432, the example in Fig. 5 shows a control loop and a control loop that can be started at any predefined period.

Claims

A transmission control method for a vehicle, comprising: determining a target transmission ratio from the rotational speed of a transmission input shaft (22) to the rotational speed of a transmission output shaft (24) in response to a signal in a first state, independent of any accelerator pedal position and dependent on a vehicle speed and a torque request from the drive axle when the axle torque request is valid, and determining the target transmission ratio in response to a signal in a second state based on the vehicle speed and an accelerator pedal position when the axle torque is not valid;controlling the opening of a first valve based on the desired gear ratio, wherein the first valve controls a transmission fluid flow to a first pulley actuator (34) and wherein the first pulley actuator (34) is connected to the transmission input shaft (22) of a continuously variable transmission (CVT) (14) and expands and contracts based on a first pressure of the transmission fluid applied to the first pulley actuator (34);and controlling the opening of a second valve based on the desired gear ratio, wherein the second valve controls a transmission fluid flow to the second pulley actuator (36), and wherein the second pulley actuator (36) is connected to the transmission output shaft (24) of the CVT (14) and expands and contracts based on a second pressure of the transmission fluid applied to the second pulley actuator (36), and wherein one of (i) a belt (38) and (ii) a chain (38) surrounds the first and second pulley actuators (34, 36). Transmission control method according to claim 1, further comprising determining the target transmission ratio, as a response to the signal in the first state, as a function of the vehicle speed and the torque requirement of the drive axle using a lookup table that relates vehicle speeds and torque requirements of the drive axle to target transmission ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. Transmission control method according to claim 2, further comprising selecting the lookup table from several lookup tables for drive modes, based on the respective drive mode of the vehicle, wherein each of the several lookup tables relates the vehicle speeds and torque requirements of the drive axle to target ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. Transmission control method according to claim 2, further comprising the determination of the target transmission ratio as a reaction to the signal in a second state, independent of the torque requirement of the drive axle and depending on the vehicle speed and the accelerator pedal position. Transmission control method according to claim 4, further comprising determining the target transmission ratio as a response to the signal in the second state, depending on the vehicle speed and the accelerator pedal position, using a second lookup table that relates vehicle speeds and accelerator pedal positions to target transmission ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. Transmission control method according to claim 5, further comprising selecting the second lookup table from several second lookup tables for drive modes, based on the respective drive mode of the vehicle, wherein each of the several second lookup tables relates the vehicle speeds and accelerator pedal positions to target ratios of the speed of the transmission input shaft to the speed of the transmission output shaft. Transmission control method according to claim 1, further comprising determining the target gear ratio as a function of the vehicle speed and the torque requirement of the drive axle in response to the determinations that the signal is in the first state and that a configuration display stored in memory indicates that the vehicle is configured to determine the target gear ratio as a function of the vehicle speed and the torque requirement of the drive axle. Transmission control method according to claim 7, further comprising determining the target gear ratio independently of the torque requirement of the drive axle and depending on the vehicle speed and the accelerator pedal position in response to the determination that the configuration display indicates that the vehicle is not configured to determine the target gear ratio depending on the vehicle speed and the torque requirement of the drive axle. Transmission control method according to claim 1, further comprising determining the target transmission ratio as a function of the vehicle speed and the torque requirement of the drive axle in response to the signal being in the first state for longer than a predetermined period.

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