PUMP SHIFT CONTROL METHOD FOR CONTINUOUSLY VARIABLE TRANSMISSIONS

Abstract

Transmission fluid control method for a vehicle, comprising: Determining a target gear ratio between a speed of an input shaft (22) and a speed of an output shaft (24) of a continuously variable transmission (CVT) (14) based on an accelerator pedal position (212); Determining a maximum rate of change (ROC) of the target ratio (312); and based on a comparison of the maximum ROC of the target ratio (312) and an ROC of the target ratio (210), selectively actuating a switching valve (120) of the CVT (14) either (i) from a closed position to an open position or (ii) from the open position to the closed position, wherein, when the switching valve (120) is in the closed position, the switching valve (120): prevents transmission fluid flow through a flow path between a transmission fluid pump (104) and a pressure control valve (116) of the CVT (14); and returns transmission fluid flow to the transmission fluid pump (104), wherein the switching valve (120) allows transmission fluid flow through the flow path when the switching valve (120) is in the open position; and wherein the transmission fluid pump (104) continues to pump transmission fluid to the pressure control valve (116) through a second flow path (i) when the switching valve (120) is in the open position and (ii) when the switching valve (120) is in the closed position.

Description

TECHNICAL FIELD

[0001] The present invention relates to vehicle transmissions and, more particularly, to methods for controlling the switching of a transmission fluid pump of a continuously variable transmission. BACKGROUND

[0002] The background description provided herein is intended to provide a general context for the disclosure. The work of the presently identified inventors within the scope described in this Background section, as well as aspects of the description not otherwise considered prior art at the time of filing, are not expressly or impliedly considered prior art to the present disclosure.

[0003] An engine generates torque that is delivered to a transmission. A vehicle's automatic transmission may include a plurality of fluid-controlled friction elements, such as clutches. A control module may engage and disengage one or more clutches according to a predetermined pattern to establish various gear ratios (also called speed ratios) within the transmission.

[0004] The transmission includes a transmission fluid pump. The transmission fluid pump supplies transmission fluid for operating the transmission clutches, lubricating transmission components, and cooling transmission components. Some transmission fluid pumps are mechanically driven, such as by the engine. Other transmission fluid pumps are electrically driven.

[0005] US 4 628 773 A discloses a transmission fluid control method for a vehicle, comprising: determining a target ratio between a speed of an input shaft and a speed of an output shaft of a continuously variable transmission based on an accelerator pedal position, selectively actuating a continuously variable control valve either from a closed position to an open position or vice versa, wherein, when the continuously variable control valve is in the closed position, it prevents transmission fluid flow through a flow path between a transmission fluid pump and a pressure control valve of the continuously variable transmission and redirects transmission fluid flow to the transmission fluid pump, and wherein the continuously variable control valve allows a transmission fluid flow to flow through the flow path when the continuously variable control valve is in the open position.

[0006] The document DE 103 16 439 A1 discloses a method for controlling a continuously variable transmission, in which the occurrence of slip is inferred when a minimum adjustment speed required for a gear ratio change of the continuously variable transmission is undershot, wherein the adjustment speed of the gear ratio change may correspond to a maximum change rate in order to avoid slip.

[0007] JP 2001-330 118 A discloses a hydraulic control device for controlling a continuously variable transmission, in which the temperature of hydraulic fluid and the rotational speed of a hydraulic pump are detected and a rate of change of a gear ratio of the continuously variable transmission is limited depending thereon.

[0008] The object of the invention is to reduce the fuel consumption of a vehicle with a continuously variable transmission.

[0009] This object is achieved by the transmission fluid control method according to claim 1. Advantageous developments of the invention are the subject of the subclaims. SUMMARY

[0010] A function describes a transmission control system of a vehicle. A target module determines a target ratio between an input shaft speed and an output shaft speed of a continuously variable transmission (CVT) based on an accelerator pedal position. A maximum rate of change (ROC) module determines a maximum ROC of the target ratio. A shift valve control module selectively actuates a shift valve of the CVT either (i) from a closed position to an open position or (ii) from the open position to the closed position based on a comparison of the maximum ROC and an ROC of the target ratio. The shift valve also returns transmission fluid to a transmission fluid pump when the shift valve is in the closed position.The shift valve prevents transmission fluid flow through a flow path between the transmission fluid pump and a pressure control valve of the CVT when the shift valve is in the closed position. The shift valve allows transmission fluid flow through the shift valve flow path when the shift valve is in the open position.

[0011] In further functions, the transmission fluid pump continues to pump transmission fluid through a second flow path to the pressure control valve, (i) both when the switching valve is in the open position and (ii) when the switching valve is in the closed position.

[0012] In other functions, the shift valve control module switches the CVT's shift valve from the closed position to the open position when the ROC of the target gear ratio is greater than the maximum ROC.

[0013] In other functions, the shift valve control module selectively switches the CVT shift valve from the open position to the closed position when the ROC of the target gear ratio is less than the maximum ROC.

[0014] In further functions, the shift valve control module selectively switches the CVT shift valve from the open position to the closed position when the ROC of the target ratio is less than at least one other maximum ROC of the target ratio for the case when the shift valve is in the closed position.

[0015] In further functions, a target pressure module determines, based on the target gear ratio, (i) a first target transmission fluid pressure on a first pulley actuator and (ii) a second target transmission fluid pressure on a second pulley actuator. The first pulley actuator is connected to the transmission input shaft of the continuously variable transmission (CVT) and expands and contracts based on a first transmission fluid pressure on the first pulley actuator. The second pulley actuator is connected to the transmission output shaft of the CVT and expands and contracts based on a second transmission fluid pressure on the second pulley actuator. Either a (i) belt or a (ii) chain surrounds the first and second pulley actuators.

[0016] In further functions, a first pulley valve control module controls the opening of a first valve based on the first desired pressure. The first valve receives transmission fluid from the pressure regulating valve and controls the flow of the transmission fluid to the first pulley actuator. A second pulley valve control module controls the opening of a second valve based on the second desired pressure. The second valve receives transmission fluid from the pressure regulating valve and controls the flow of the transmission fluid to the second pulley actuator.

[0017] In other functions, a module indicates an upshift when a change in the target ratio is greater than a predetermined value and determines a second maximum ROC of the target ratio that can occur between a start and a finish of the upshift. The maximum ROC module determines the maximum ROC of the target ratio for the upshift. The shift valve control module selectively actuates the CVT shift valve from the closed position to the open position when the second maximum ROC is greater than the maximum ROC.

[0018] In other functions, a module indicates a downshift when a change in the target ratio is greater than a predetermined value and determines a second maximum ROC of the target ratio that can occur between a start and a finish of the downshift. The maximum ROC module determines the maximum ROC of the target ratio for the downshift. The shift valve control module selectively actuates the CVT shift valve from the closed position to the open position when the second maximum ROC is greater than the maximum ROC.

[0019] In additional functionality, a shift module indicates that no shift has been commanded when a change in the target gear ratio is less than a predetermined value. The target module further determines a desired ROC of the target gear ratio based on the accelerator pedal position. If no shift has been commanded, the shift valve control module actuates the shift valve from the closed position to the open position if the target ROC is greater than the maximum ROC. If no shift has been commanded, the shift valve control module actuates the shift valve from the open position to the closed position if the target ROC is less than the maximum ROC.

[0020] In one feature, a transmission fluid control method is described. The transmission fluid control method includes: determining a desired ratio between a speed of an input shaft and a speed of an output shaft of a continuously variable transmission (CVT) based on an accelerator pedal position; determining a maximum rate of change (ROC) of the desired ratio; and based on a comparison of the maximum ROC and an ROC of the desired ratio, selectively actuating a shift valve of the CVT from either (i) a closed position to an open position or (ii) from the open position to the closed position. The shift valve prevents transmission fluid flow through a flow path between a transmission fluid pump and a pressure control valve of the CVT when the shift valve is in the closed position. The shift valve also returns transmission fluid to the transmission fluid pump when the shift valve is in the closed position.The shift valve allows transmission fluid flow through the flow path when the shift valve is in the open position.

[0021] In further functions, the transmission fluid pump continues to pump transmission fluid through a second flow path to the pressure control valve both (i) when the switching valve is in the open position and (ii) when the switching valve is in the closed position.

[0022] In further functions, the transmission fluid control method further includes selectively transitioning the CVT shift valve from the closed position to the open position when the ROC of the target gear ratio is greater than the maximum ROC.

[0023] In further functions, the transmission fluid control method further includes selectively transitioning the CVT shift valve from the open position to the closed position when the ROC of the target gear ratio is less than the maximum ROC.

[0024] In further functions, the transmission fluid control method further includes selectively transitioning the CVT shift valve from the open position to the closed position when the ROC of the target ratio is less than at least one other maximum ROC of the target ratio for a case when the shift valve is in the closed position.

[0025] In further features, the transmission fluid control method includes determining, based on the desired gear ratio, (i) a first desired transmission fluid pressure on a first pulley actuator and (ii) a second desired transmission fluid pressure on a second 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 transmission fluid pressure on the first pulley actuator. The second pulley actuator is connected to the transmission output shaft of the CVT and expands and contracts based on a second transmission fluid pressure on the second pulley actuator. Either (i) a belt or (ii) a chain surrounds the first and second pulley actuators.

[0026] In further features, the transmission fluid control method includes: controlling opening of a first valve based on the first desired pressure, wherein the first valve receives transmission fluid from the pressure regulating valve and controls transmission fluid flow to the first pulley actuator; and controlling opening of a second valve based on the second desired pressure, wherein the second valve receives transmission fluid from the pressure regulating valve and controls transmission fluid flow to the second pulley actuator.

[0027] In further features, the transmission fluid control method includes: indicating an upshift when a change in the target gear ratio is greater than a predetermined value; determining a second maximum ROC of the target gear ratio that may occur between a beginning and an end of the upshift, wherein determining the maximum ROC includes determining the maximum ROC of the target gear ratio for the upshift; and selectively actuating the shift valve of the CVT from the closed position to the open position when the second maximum ROC is greater than the maximum ROC.

[0028] In further features, the transmission fluid control method includes: indicating a downshift when a change in the target gear ratio is greater than a predetermined value; determining a second maximum ROC of the target gear ratio that may occur between a beginning and an end of the downshift, wherein determining the maximum ROC includes determining the maximum ROC of the target gear ratio for the downshift; and selectively actuating the shift valve of the CVT from the closed position to the open position when the second maximum ROC is greater than the maximum ROC.

[0029] In further functions, the transmission fluid control method includes: indicating that no shift has been commanded when a change in the target gear ratio is less than a predetermined value; determining a desired ROC of the target gear ratio based on the accelerator pedal position; when no shift has been commanded, actuating the shift valve from the closed position to the open position when the desired ROC is greater than the maximum ROC; and, when no shift has been commanded, actuating the shift valve from the open position to the closed position when the desired ROC is less than the maximum ROC.

[0030] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present disclosure will become more fully understood with reference to the detailed description and the accompanying drawings: Fig. 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 maximum module; and Fig. 5 is a flowchart of an exemplary method for controlling a transmission fluid pump switching valve.

[0032] In the drawings, the same reference numerals are used for similar and / or identical elements. DETAILED DESCRIPTION

[0033] An engine generates drive torque for a vehicle. A continuously variable transmission (CVT) transfers torque to one or more of the vehicle's wheels. A transmission fluid pump pumps transmission fluid through a second flow path to a line pressure control valve. The transmission fluid pump also pumps transmission fluid to a switching valve in a first flow path between the transmission fluid pump and the line pressure control valve. The switching valve can open to provide a first transmission fluid flow rate to the line pressure control valve and can be closed to provide a portion (e.g., one-half) of the first transmission fluid flow rate to the line pressure control valve while recirculating the other portion to the transmission pump suction side. A fuel efficiency improvement can be realized when the switching valve is closed due to a reduced load on the transmission fluid pump.

[0034] The CVT includes a primary pulley and a secondary pulley. The primary pulley is coupled to an input shaft, and the secondary pulley is coupled to an output shaft. Torque is transmitted to one or more of the vehicle's wheels via the output shaft. A belt or chain encircles the primary and secondary pulleys.

[0035] The primary pulley includes a primary pulley actuator that expands and contracts based on transmission fluid pressure applied to the primary pulley actuator and centrifugal force. The secondary pulley includes a secondary pulley actuator that expands and contracts based on transmission fluid pressure applied to the secondary pulley actuator, centrifugal force, and spring force. The primary and secondary pulley actuators vary a speed ratio between the input and output shafts of the CVT via expansion and contraction.

[0036] A control module controls the pressures applied to the primary and secondary pulley actuators based on a desired gear ratio between the CVT's input and output shafts. Various constraints can limit how quickly the desired gear ratio can change. Examples of constraints include pressure constraints and transmission fluid pump constraints.

[0037] According to the present invention, the control module determines maximum rates of change of the gear ratio for various constraints and controls the switching valve based on the maximum rates of change. For example, the control module may transition the switching valve from the closed position to the open position when a desired rate of change of the gear ratio is greater than one or more of the maximum rates of change. The control module may transition the switching valve from the open position to the closed position when the desired rate of change is lower than all maximum rates of change for operation with the switching valve in the closed position.

[0038] Fig. 1A and Fig. 1B include 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 may, for example, be a gasoline engine, a diesel engine, or another suitable engine type. A vehicle may also include one or more electric motors and / or motor-generator units (MGUs), such as MGU 18.

[0039] The engine 12 transmits torque to the torque converter 16 via an engine output shaft 20, such as a crankshaft. The torque converter 16 supplies torque to the transmission 14 via a transmission input shaft 22. In some cases, the torque converter 16 may be omitted. The electric motor(s) and / or MGU(s) may also transmit torque to the transmission input shaft 22 to supplement or replace engine torque output. An MGU can convert mechanical energy to electrical energy under certain circumstances, for example, to recharge one or more batteries and / or to provide power to electronic components of the vehicle.

[0040] The transmission 14 transmits torque between the transmission input shaft 22 and a transmission output shaft 24. The input ratio may refer to or be based on the ratio between the speed of the transmission input shaft 22 and the 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 of the transmission 14. The mode may include, for example, a park mode, a reverse mode, a neutral mode, or one or more forward drive modes.

[0041] 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 that expands and contracts based on transmission fluid pressure applied to the primary pulley actuator 34. The secondary pulley 32 includes a secondary pulley actuator 36 that expands and contracts based on transmission fluid pressure applied to the secondary pulley actuator 36. While the example of the primary pulley 30 being directly coupled to the transmission input shaft 22 is provided, the primary pulley 30 may be indirectly coupled to the transmission input shaft 22 via one or more torque transmitting devices.Also, while the example of the secondary pulley 32 is provided as being directly coupled to the transmission output shaft 24, the secondary pulley 32 may be indirectly coupled to the transmission output shaft 24 via one or more torque transmitting devices.

[0042] As in Fig. As shown in Figure 1B, a belt or chain 38 surrounds the primary and secondary pulleys 30 and 32 for rotating the transmission input shaft 22 and the transmission output shaft 24. The expansion and contraction of the primary and secondary pulley actuators 34 and 36 varies the rotational ratio between the transmission input shaft 22 and the transmission output shaft 24.

[0043] An engine control module (ECM) 60 controls the operation of the engine 12. The ECM 60 or another control module (not shown) may 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 as being implemented within the transmission 14, the TCM 70 may be implemented outside the transmission 14 in various applications. The ECM 60 and the TCM 70 may share data.

[0044] With reference to Fig. 2, a functional block diagram of an exemplary use of the CVT system is presented. The CVT 14 includes a transmission fluid pump 104 that draws transmission fluid from a reservoir 112 or other suitable transmission fluid source. The transmission fluid pump 104 is mechanically driven by the engine 12, such as by rotation of the crankshaft 20 or the transmission input shaft 22.

[0045] The transmission fluid pump 104 transfers the transmission fluid to a pressure control valve 116 via a first fluid channel. The transmission fluid pump 104 also transfers the transmission fluid to a switching valve 120 via a second fluid channel. 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 control valve 116. In various applications, the switching valve 120 can be integrated within the transmission fluid pump 104. When the switching valve 120 is closed, the second fluid channel is connected back to the pump sump.

[0046] The pressure regulating valve 116 regulates the flow of transmission fluid to a primary pulley valve 124, a secondary pulley valve 128, and / or one or more other actuators / functions 132. The pressure regulating valve 116 also regulates the flow and / or pressure of transmission fluid output to other actuators / functions 134 via a separate fluid channel. The other actuators and / or functions 132 and 134 may include, for example, the torque converter 16 (e.g., clutch), one or more variable solenoid blowoff valves (VFS) that regulate transmission fluid flow and pressure to the various valves and components, cool the CVT 14, and / or lubricate the components of the CVT 14. An output pressure of the pressure regulating valve 116 may be described as line pressure 122.

[0047] The primary pulley valve 124 regulates the flow (and pressure) of transmission fluid to the primary pulley actuator 34. For example, the primary pulley valve 124 may be opened to increase transmission fluid flow to the primary pulley actuator 34, expanding the primary pulley actuator 34. The primary pulley valve 124 may be closed to decrease transmission fluid flow to the primary pulley actuator 34, contracting the primary pulley actuator 34. An output pressure of the primary pulley valve 124 may be described as primary pulley pressure 126.

[0048] The secondary pulley valve 128 regulates the flow (and pressure) of transmission fluid to the secondary pulley actuator 36. For example, the secondary pulley valve 128 can be opened to increase transmission fluid flow to the secondary pulley actuator 36, expanding the secondary pulley actuator 36. The secondary pulley valve 128 can be closed to decrease transmission fluid flow to the secondary pulley actuator 36, contracting the secondary pulley actuator 36. An output pressure of the secondary pulley valve 128 can be described as secondary pulley pressure 136. The corresponding VBS or VFS valves (not shown), for example, can be used to control the flow / pressure of transmission fluid from the shift valve 120, the primary and secondary pulley valves 124 and 128, and the pressure control valve 116.

[0049] A fluid control module 150 controls the actuation of the switching valve 120, the pressure control valve 116, the primary pulley valve 124, and the secondary pulley valve 128. Generally, the fluid control module 150 actuates the switching valve 120 to one of two discrete positions at a given time: an open position or a closed position. The fluid control module 150 switches the switching valve 120 between the two discrete positions under certain circumstances.

[0050] When the switching valve 120 is in the closed position, the transmission fluid pump 104 operates in partial mode (e.g., half-mode). The switching valve 120 blocks transmission fluid flow through the second fluid passage in the closed position, so that the transmission fluid pump 104 pumps transmission fluid only through the first fluid passage to the pressure control valve 116. Because the transmission fluid pump 104 is driven by the engine 12, a fuel efficiency improvement (i.e., a fuel consumption reduction) of the engine 12 (compared to full-mode operation) may be realized during partial mode operation because the transmission fluid pump 104 exerts a lower torque load on the engine 12.

[0051] When the switching valve 120 is in the open position, the transmission fluid pump 104 operates in full-mode operation. The switching valve 120 enables transmission fluid flow through the second fluid passage when in the open position, so that the transmission fluid pump 104 pumps transmission fluid through the first and second fluid passages to the pressure control valve 116.

[0052] The fluid control module 150 can transfer the switching valve 120 from the closed position to the open position under various circumstances. For example, the fluid control module 150 can only switch the switching valve 120 from the closed position to the open position when a change in the target gear ratio between the input and output shafts 22 and 24 is greater than a predetermined value. The fluid control module 150 can switch the switching valve 120 from the open position to the closed position under various circumstances. For example, the fluid control module 150 can only switch the switching valve 120 from the closed position to the open position when a change in the target gear ratio between the input and output shafts 22 and 24 is greater than a predetermined value.

[0053] With reference to Fig. 3, a functional block diagram of an exemplary transmission fluid control system is shown. The fluid control module 150 may be implemented independently within the transmission control module (TCM) 70 or within other suitable modules.

[0054] A desired gear ratio module 204 determines a desired gear ratio (between the input and output shafts 22 and 24) and a desired rate of change (ROC) 210 of the desired gear ratio to be achieved using the primary and secondary pulley actuators 34 and 36. The desired gear ratio module 204 may determine the desired gear ratio and the desired ROC 210 of the desired gear ratio based, for example, on an accelerator pedal position (APP) 212, a vehicle speed 216, and / or one or more appropriate parameters.

[0055] The target gear ratio module 204 may determine the target gear ratio and the target ROC 210 of the target gear ratio, for example, using one or more lookup tables or functions that link the APP 212 and the vehicle speed 216 to the target gear ratio and the target ROC 210 of the target gear ratio.

[0056] A first target pressure module 220 determines a primary pulley target pressure 224 and a secondary pulley target pressure 228 based on the target gear ratio and the target ROC 210 of the target gear ratio. The primary pulley target pressure 224 corresponds to a primary pulley pressure target 126. The secondary pulley target pressure 228 corresponds to a secondary pulley pressure target 136. The first target pressure module 220 may set the primary pulley pressure 224 and the secondary pulley pressure 228, for example, using one or more lookup tables or functions that link the target gear ratio and / or the target ROC 210 of the target gear ratio to the primary pulley target pressure 224 and the secondary pulley pressure 228.

[0057] A primary valve control module 232 controls the opening of the primary pulley valve 124 based on the primary pulley target pressure 224. The primary valve control module 232 may, for example, control the opening of the primary pulley valve 124 in a closed-loop manner based on the difference between the primary pulley target pressure 224 and a measured or estimated value of the primary pulley pressure 126. For example, the primary valve control module 232 may open the primary pulley valve 124 as the primary pulley target pressure 224 increases, and vice versa, under certain circumstances.

[0058] A secondary valve control module 236 controls the opening of the secondary pulley valve 128 based on the secondary pulley target pressure 228. The secondary valve control module 236 may, for example, control the opening of the secondary pulley valve 128 in a closed-loop manner based on the difference between the secondary pulley target pressure 228 and a measured or estimated value of the secondary pulley pressure 136. For example, the secondary valve control module 236 may open the secondary pulley valve 128 as the secondary pulley target pressure 228 increases and, under certain circumstances, reverses.

[0059] A switching valve control module 240 controls the actuation of the switching valve 120. As mentioned above, the switching valve 120 is operated in either the open position or the closed position. The switching valve control module 240 selectively switches the switching valve 120 from the open position to the closed position and from the closed position to the open position, as discussed further below.

[0060] A control valve control module 252 controls the opening of the pressure control valve 116 based on a set desired line pressure 256. The set desired line pressure 256 corresponds to a setpoint of the line pressure 122. For example, the control valve control module 252 can open the pressure control valve 116 when the set desired line pressure 256 increases and vice versa, under certain circumstances.

[0061] An adjustment module 260 sets a desired line pressure 264 based on a pressure adjustment 268 to achieve the set desired line pressure 256. For example, the adjustment module 260 may set the set desired line pressure 256 equal to or based on a sum or product of (a) the desired line pressure 264 and (b) the pressure adjustment 268.

[0062] A second desired pressure module 272 determines the desired line pressure 264. For example, the second desired pressure module 272 may receive one or more desired line pressure requests 276 and set the desired line pressure 264 equal to or based on one of the highest (maximum) desired line pressure requests 276. Desired line pressure requests may be generated for various reasons and for various actuators. For example, a desired line pressure request may be generated to achieve the desired gear ratio, control the torque converter clutch, lubrication, and / or cooling.

[0063] An adjustment determination module 280 determines the pressure adjustment 268. The adjustment determination module 280 may set the pressure adjustment 268 to a predetermined value under certain circumstances. The adjustment module 260 sets the adjusted desired line pressure 256 equal to the desired line pressure 264 when the pressure adjustment 268 is set to the predetermined value. For example, the predetermined value may be 0.0 in the example of the adjustment module 260 setting the desired line pressure 256 to a sum of the desired line pressure 264 and the pressure adjustment 268. In the example of the adjustment module 260 setting the adjusted desired line pressure 256 to a product of the desired line pressure 264 and the pressure adjustment 268, the predetermined value may be 1.0.

[0064] The adjustment determination module 280 may determine the pressure adjustment 268 based on a maximum target pressure 284 under special circumstances, such as when the switching valve control module switches the switching valve 120 from the closed position to the open position. The adjustment determination module 280 may also determine the pressure adjustment 268 based on the maximum target pressure 284 when the switching valve control module switches the switching valve 120 from the open position to the closed position. The adjustment determination module 280 may determine the pressure adjustment 268 based on the maximum target pressure 284 using one or more lookup tables that link maximum target pressures to pressure adjustments.

[0065] A maximum module 292 determines the maximum target pressure 284 based on the primary pulley target pressure 224, the secondary pulley target pressure 228, and the target line pressure 264. For example, the maximum module 292 may set the maximum target pressure 284 to be equal to or based on a highest (maximum) primary pulley target pressure 224, the secondary pulley target pressure 228, and the target line pressure 264.

[0066] An opening module 296 generates an opening signal 300 when one or more conditions for switching the switching valve 120 to the open position are present. For example, the opening module 296 may generate the opening signal 300 when a request is received to move the switching valve 120 to the open position. A service device / tool ​​may be connected to the vehicle, for example, via a diagnostic (OBD) port of the vehicle, and transmit the service request. Additionally or alternatively, the opening module 296 may generate the opening signal 300 when one or more predetermined faults have been diagnosed. Additionally or alternatively, the opening module 296 may generate the opening signal 300 when a position of a brake pedal is higher than a predetermined position or a depression rate of the brake pedal is greater than a predetermined rate.While three exemplary conditions have been provided, the opening module 296 may generate the opening signal 300 when one or more other conditions occur.

[0067] The switching valve control module 240 switches the switching valve 120 from the closed position to the open position when the opening signal 300 is generated. If the switching valve 120 is already in the open position, the switching valve control module 240 may maintain the switching valve 120 in the open position when the opening signal 300 is generated. The opening signal 300 may be used to override normal control of the switching valve 120. If the opening signal 300 is not generated, the switching valve control module 240 may control the switching valve 120 using normal control, as discussed below.

[0068] “Shifting,” such as upshifting and downshifting, may refer to a change in the target gear ratio that is greater than a predetermined value. A shift module 304 generates a shift signal 308 indicating whether an upshift, a downshift, or no shift has been commanded by a driver. For example, the shift module 304 may set the shift signal 308 to indicate that an upshift has been commanded when the target gear ratio increases by at least a predetermined upshift value. The shift module 304 may set the shift signal 308 to indicate that a downshift has been commanded when the target gear ratio decreases by at least a predetermined downshift value. The shift module 304 may set the shift signal 308 to indicate that no shift has been commanded when neither an upshift nor a downshift has been commanded.

[0069] The predetermined upshift and downshift values ​​may be fixed or variable. For example, the predetermined upshift and downshift values ​​may vary based on the current speed ratio of the transmission input shaft 22 and the transmission output shaft 24. The shift module 304 may determine the predetermined upshift and downshift values, for example, using one or more lookup tables that relate current gear ratios to predetermined upshift and downshift values.

[0070] The shift module 304 also determines a maximum ROC 312 of the target gear ratio for upshifts and downshifts. The maximum ROC 312 for a shift (upshift or downshift, respectively) corresponds to a maximum ROC of the target gear ratio that may occur between a start of the shift and an end of the shift. The shift module 304 may determine the maximum ROC 312 for the shift based, for example, on a previous value of the target gear ratio before the shift was commanded, the target gear ratio that indicated that the shift was commanded, the ROC of the APP 212, the vehicle speed 216, and / or one or more appropriate parameters. The shift module 304 may determine the maximum ROC 312, for example, using one or more lookup tables or functions that relate the previous value of the target gear ratio, the target gear ratio, the ROC of the APP 212, and the vehicle speed 216 to the maximum ROC 312.

[0071] Two constraints on target gear ratio changes include constraints on transmission fluid pressure at the primary and secondary pulley actuators 34 and 36 and constraints on fluid flow to the primary and secondary pulley actuators 34 and 36. For example, constraints on transmission fluid pressure at the primary and secondary pulley actuators 34 and 36 may be attributed to line pressure 122 and constraints on primary and secondary pulley pressures 126 and 136. For example, constraints on transmission fluid flow to the primary and secondary pulley actuators 34 and 36 may be attributed to transmission fluid pump 104.

[0072] A maximum ROC module 316 determines a plurality of maximum ROCs 318 of the desired ratio for upshifts, downshifts, line pressure restrictions, pulley pressure restrictions, operating with the shift valve 120 in the open position, and operating with the shift valve 120 in the closed position. The shift valve control module 240 may switch the shift valve 120 to the closed position or the open position based on one or more of the maximum ROCs 318, the desired ROC 210, and / or the maximum ROC 312, as discussed below.

[0073] Fig. 4 shows a functional block diagram illustrating an example use of the maximum ROC module 316. A first upshift maximum module 320 determines a first maximum upshift ROC 324 of the target ratio. The first maximum upshift ROC 324 corresponds to the maximum ROC of the target ratio based on a maximum value of the line pressure 122 during an upshift. The first upshift maximum module 320 also determines a second maximum upshift ROC 328 of the target ratio. The second maximum upshift ROC 328 corresponds to the maximum ROC of the target ratio based on a maximum value of the primary pulley pressure 126 during an upshift.

[0074] The first upshift maximum module 320 determines the first and second maximum upshift ROCs 324 and 328 based on a steady-state primary pulley pressure, a maximum primary pulley pressure, a maximum line pressure, and a ratio maintenance value. The steady-state primary pulley pressure may correspond to a required pressure to maintain torque on the primary pulley 30 at a speed ratio of the transmission input shaft 22 to the speed of the transmission output shaft 24. The maximum primary pulley pressure may correspond to a maximum value of the primary pulley pressure 126 and may be a predetermined value. The maximum line pressure may correspond to a maximum value of the line pressure 122 and may be a predetermined value.The ratio maintenance value may correspond to a ratio of a net force on the primary pulley 30 to a net force on the secondary pulley 32 to maintain a speed ratio of the transmission input shaft 22 to the speed of the transmission output shaft 24. The ratio maintenance value may be determined based on the ratio of the speed of the transmission input shaft 22 to the speed of the transmission output shaft 24, the primary pulley pressure 126 to a minimum value of the primary pulley pressure to maintain the ratio, and the secondary pulley pressure 136 to a minimum value of the primary pulley pressure to maintain the ratio.

[0075] The first upshift maximum module 320 may further determine the first and second maximum upshift ROCs 324 and 328 based on a transmission fluid temperature and a current ratio of the speed of the transmission input shaft 22 to the speed of the transmission output shaft 24. The transmission fluid temperature may be measured using a transmission fluid temperature sensor. The current ratio of the speed of the transmission input shaft 22 to the speed of the transmission output shaft 24 may be determined, for example, based on a ratio of a measured speed of the transmission input shaft 22 and a measured speed of the transmission output shaft 24.

[0076] The stationary primary pulley pressure, the maximum primary pulley pressure, the maximum line pressure and the ratio maintenance value, the transmission fluid temperature and the current ratio are together in Fig. 4 by the inputs 332. The first upshift maximum module 320 may determine the first maximum upshift ROC 324 using one or more functions or lookup tables that relate the values ​​of the inputs to the first maximum upshift ROC. The first upshift maximum module 320 may determine the second maximum upshift ROC 328 using one or more functions or lookup tables that relate the values ​​of the inputs to the second maximum upshift ROC.

[0077] A first minimum module 336 selects a minimum (smaller) of the first and second maximum upshift ROCs 324 and 328. The first minimum module 336 outputs the selected one of the first and second maximum upshift ROCs 324 and 328 as a third maximum upshift ROC 340.

[0078] A first downshift maximum module 344 determines a first maximum downshift ROC 348 of the target ratio. The first maximum downshift ROC 348 corresponds to the maximum ROC in the target ratio based on a maximum value of the line pressure 122 during a downshift. The first downshift maximum module 344 also determines a second maximum downshift ROC 352 in the target ratio. The second maximum downshift ROC 352 corresponds to the maximum ROC in the target ratio based on a maximum value of the secondary pulley pressure 136 during a downshift.

[0079] The first downshift maximum module 344 determines the first and second maximum downshift ROCs 348 and 352 based on a steady-state secondary pulley pressure, a maximum secondary pulley pressure, the maximum line pressure, and the ratio maintenance value. The maximum secondary pulley pressure may be the same as the maximum primary pulley pressure. The steady-state secondary pulley pressure may correspond to a pressure at the secondary pulley actuator 36 for maintaining a ratio (the transmission input shaft speed versus the transmission output shaft speed) when the primary pulley pressure 126 is a predetermined pressure.

[0080] The first downshift maximum module 344 may further determine the first and second maximum downshift ROCs 348 and 352 based on the transmission fluid temperature and the current ratio of the speed of the transmission input shaft 22 to the speed of the transmission output shaft 24. The steady-state secondary pulley pressure, the maximum secondary pulley pressure, the maximum line pressure, and the ratio maintenance value, the transmission fluid temperature, and the current ratio are collectively included in Fig. 4 via inputs 354. The first downshift maximum module 344 may determine the first maximum downshift ROC 348 using one or more functions or lookup tables that associate values ​​of the inputs with the first maximum downshift ROC. The first downshift maximum module 344 may determine the second maximum downshift ROC 352 using one or more functions or lookup tables that associate values ​​of the inputs with the second maximum downshift ROC.

[0081] A second minimum module 356 selects a minimum (smaller) of the first and second maximum downshift ROCs 348 and 352. The second minimum module 356 outputs the selected one of the first and second maximum downshift ROCs 348 and 352 as a third maximum downshift ROC 360.

[0082] A second upshift maximum module 364 determines a fourth maximum upshift ROC 368 of the target ratio for the shift valve 120 in the closed position (i.e., partial mode operation). The fourth maximum upshift ROC 368 corresponds to the maximum ROC of the target ratio during an upshift with the shift valve 120 in the closed position. The second upshift maximum module 364 also determines a fifth maximum upshift ROC 372 of the target ratio. The fifth maximum upshift ROC 372 corresponds to the maximum ROC of the target ratio during an upshift with the shift valve 120 in the open position (i.e., full mode operation).

[0083] The second upshift maximum module 364 determines the fourth and fifth maximum upshift ROCs 368 and 372 based on an engine speed, primary pulley pressure, pressure adjustment 268, transmission fluid temperature, and a torque converter clutch condition. The engine speed may be measured, for example, with an engine speed sensor. The torque converter clutch condition may be slipping or non-slipping (locked), for example.

[0084] The stationary primary pulley pressure, engine speed, transmission fluid temperature, torque converter clutch condition, and pressure adjustment 268 are collectively in Fig. 4 via inputs 376. The second upshift maximum module 364 may determine the fourth maximum upshift ROC 368 using one or more functions or lookup tables that associate values ​​of the inputs with the fourth maximum upshift ROC. The second upshift maximum module 364 may determine the fifth maximum upshift ROC 372 using one or more functions or lookup tables that associate values ​​of the inputs with the fifth maximum upshift ROC.

[0085] A second downshift maximum module 380 determines a fourth maximum downshift ROC 384 at the desired ratio for the shift valve 120 in the closed position (i.e., partial mode operation). The fourth maximum downshift ROC 384 corresponds to the maximum ROC of the desired ratio during a downshift with the shift valve 120 in the closed position. The second downshift maximum module 380 also determines a fifth maximum downshift ROC 388 of the desired ratio. The fifth maximum downshift ROC 388 corresponds to the maximum ROC of the desired ratio during a downshift with the shift valve 120 in the open position (i.e., full mode operation).

[0086] The second downshift maximum module 380 determines the fourth and fifth maximum downshift ROCs 384 and 388 based on the engine speed, the secondary pulley pressure, the pressure adjustment 268, the transmission fluid temperature, and the torque converter clutch condition. The steady-state secondary pulley pressure, the engine speed, the transmission fluid temperature, the torque converter clutch condition, and the pressure adjustment 268 are collectively included in Fig. 4 via inputs 392. The second downshift maximum module 380 may determine the fourth maximum downshift ROC 384 using one or more functions or lookup tables that associate values ​​of the inputs with the fourth maximum downshift ROC. The second downshift maximum module 380 may determine the fifth maximum downshift ROC 388 using one or more functions or lookup tables that associate values ​​of the inputs with the fifth maximum downshift ROC.

[0087] The shift valve control module 240 controls the shift valve 120 based on comparisons of either (i) the desired ROC 210 or (ii) the maximum ROC 312 with one or more of (i) the third maximum upshift ROC 340, (ii) the third maximum downshift ROC 360, (iii) the fourth maximum upshift ROC 368, (iv) the fifth maximum upshift ROC 372, (v) the fourth maximum downshift ROC 384, and (vi) the fifth maximum downshift ROC 388. Fig. 5 includes a flowchart illustrating an exemplary method for controlling the switching valve 120.

[0088] With reference now to Fig. 3 and Fig. 5, control begins with 504, wherein the opening module 296 determines whether one or more of the opening conditions are present. If 504 is true, the opening module 296 generates the open signal 300, and control continues with 540. The switching valve control module 240 switches the switching valve 120 to the open position or maintains the switching valve 120 in the open position at 540. If 504 is false, control continues with 508.

[0089] At 508, the maximum ROC module 316 determines the third maximum upshift ROC 340, the third maximum downshift ROC 360, the fourth maximum upshift ROC 368, the fifth maximum upshift ROC 372, the fourth maximum downshift ROC 384, and the fifth maximum downshift ROC 388. These determinations are made with reference to Fig. 4 discussed above.

[0090] At 512, the shift valve control module 240 determines whether the shift signal 308 indicates that the driver has commanded an upshift. If 512 is true, the shift valve control module 240 selects the third maximum upshift ROC 340 and the fourth maximum upshift ROC 368 for comparisons at 516, and control then continues to 532. 532 is further discussed below. If 512 is false, control continues to 520.

[0091] The shift valve control module 240 determines whether the shift signal 308 indicates that the driver has commanded a downshift at 520. If 520 is true, the shift valve control module 240 selects the third maximum downshift ROC 360 and the fourth maximum downshift ROC 384 for comparisons at 524, and control then continues to 532. If 520 is false, control continues to 528.

[0092] At 528, the switching valve control module 240 determines whether the desired ROC 210 is greater than one or more of: the third maximum upshift ROC 340, the third maximum downshift ROC 360, the fourth maximum upshift ROC 368, and the fourth maximum downshift ROC 384. If 528 is true, the switching valve control module 240 switches the switching valve 120 to the open position or maintains the switching valve 120 in the open position at 540. If 528 is false, the switching valve control module 240 switches the switching valve 120 to the closed position or maintains the switching valve 120 in the closed position at 536. In this way, the switching valve control module 240 operates the switching valve 120 in the open position when the desired ROC 210 is greater than at least one of the third maximum upshift ROC 340, the third maximum downshift ROC 360, the fourth maximum upshift ROC 368, and the fourth maximum downshift ROC 384.If neither an upshift nor a downshift has been commanded, the shift valve control module 240 uses the desired ROC 210 in the comparisons.

[0093] At 532, the shift valve control module 240 determines whether the maximum ROC 312 for the upshift or downshift is greater than one or more of the selected maximum ROCs. For example, if a downshift has been commanded, the shift valve control module 240 determines whether the maximum ROC 312 for the downshift is greater than one or more of the third maximum downshift ROC 360 and the fourth maximum downshift ROC 384. If an upshift has been commanded, the shift valve control module 240 determines whether the maximum ROC 312 for the upshift is greater than one or more of the third maximum upshift ROC 340 and the fourth maximum upshift ROC 368. If 532 is true, the shift valve control module 240 switches the shift valve 120 to the open position or maintains the shift valve 120 in the open position at 540.If 532 is false, the shift valve control module 240 switches the shift valve 120 to the closed position or maintains the shift valve 120 in the closed position at 536. In this way, the shift valve control module 240 operates the shift valve 120 in the open position when the maximum ROC 312 for a shift is greater than at least one of the maximum ROCs for that shift. The shift valve control module 240 uses the maximum ROC 312 in the comparisons when an upshift or downshift is commanded.

[0094] The foregoing description is merely illustrative and is in no way intended to limit the present disclosure, its embodiments, or uses. The broad teachings of the disclosure may be embodied in numerous forms. Thus, while the present disclosure includes specific examples, the true scope of the disclosure is in no way limited thereby, and further modifications will become apparent from a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure.Furthermore, although each of the embodiments is described above as having certain features, one or more of the features described with respect to each embodiment of the disclosure may be implemented and / or combined in any of the other embodiments, even if this combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments remain within the scope of this disclosure.

Claims

[1] Transmission fluid control method for a vehicle, comprising: Determining a target gear ratio between a speed of a drive shaft (22) and a speed of an output shaft (24) of a continuously variable transmission (CVT) (14) based on an accelerator pedal position (212); Determining a maximum rate of change (ROC) of the target translation (312); and based on a comparison of the maximum ROC of the target ratio (312) and an ROC of the target ratio (210), selective actuation of a switching valve (120) of the CVT (14) either (i) from a closed position to an open position or (ii) from the open position to the closed position, wherein, when the switching valve (120) is in the closed position, the switching valve (120): prevents transmission fluid flow through a flow path between a transmission fluid pump (104) and a pressure control valve (116) of the CVT (14); and returns transmission fluid flow to the transmission fluid pump (104), wherein the switching valve (120) allows transmission fluid flow through the flow path when the switching valve (120) is in the open position; and wherein the transmission fluid pump (104) continues to pump transmission fluid to the pressure control valve (116) through a second flow path (i) when the switching valve (120) is in the open position and (ii) when the switching valve (120) is in the closed position. [2] Transmission fluid control method according to claim 1, further comprising selectively switching the switching valve (120) of the CVT (14) from the closed position to the open position when the ROC of the target ratio (210) is greater than the maximum ROC of the target ratio (312). [3] Transmission fluid control method according to claim 1, further comprising selectively switching the switching valve (120) of the CVT (14) from the open position to the closed position when the ROC of the target ratio (210) is less than the maximum ROC of the target ratio (312). [4] Transmission fluid control method according to claim 1, further comprising selectively switching the switching valve (120) of the CVT (14) from the open position to the closed position when the ROC of the target ratio (210) is smaller than at least one other maximum ROC of the target ratio (318). [5] Transmission fluid control method according to claim 1, further comprising: based on the target transmission ratio, determining a first target pressure (224) of the transmission fluid on a first pulley actuator (34) and a second target pressure (228) of the transmission fluid on a second pulley actuator (36), wherein the first pulley actuator (34) is connected to the transmission input shaft (22) of the CVT (14) and expands and contracts based on a first pressure (126) of the transmission fluid exerted on the first pulley actuator (34), 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 (136) of the transmission fluid exerted on the second pulley actuator (36), and wherein one of a belt (38) and a chain (38) surrounds the first (34) and second (36) pulley actuator. [6] Transmission fluid control method according to claim 5, further comprising: Controlling the flow of a first valve (124) based on the first set pressure (224), wherein the first valve (124) receives transmission fluid from the pressure regulating valve (116) and controls the transmission fluid flow to the first pulley actuator (34); and Controlling the flow of a second valve (128) based on the second set pressure (228), wherein the second valve (128) receives transmission fluid from the pressure control valve (116) and controls transmission fluid flow to the second pulley actuator (36). [7] Transmission fluid control method according to claim 1, further comprising: Display an upshift when a change in the target gear ratio is greater than a predetermined value; Determining a second maximum ROC of the target gear ratio (328) that can occur between the beginning and end of an upshift, wherein determining the maximum ROC of the target gear ratio (312) includes determining the maximum ROC of the target gear ratio (328) for upshifting (328); and selective actuation of the switching valve (120) of the CVT (14) from the closed position to the open position when the second maximum ROC (328) is greater than the maximum ROC of the target ratio (312). [8] Transmission fluid control method according to claim 1, further comprising: Display a downshift when a change in the target gear ratio is greater than a predetermined value; Determining a second maximum ROC of the target gear ratio (352) that can occur between the beginning and end of a downshift, wherein determining the second maximum ROC of the target gear ratio (312) includes determining the maximum ROC of the target gear ratio for downshifting (352); and selective actuation of the switching valve (120) of the CVT (14) from the closed position to the open position when the second maximum ROC (352) is greater than the maximum ROC of the target ratio (312). [9] Transmission fluid control method according to claim 1, further comprising: Indicates that no shifting has been ordered if the change in the target gear ratio is less than a predetermined value; Determining a target ROC of the target gear ratio (210) based on the accelerator pedal position (212); If no switching has been commanded, actuate the switching valve (120) from the closed position to the open position if the target ROC is greater than the maximum ROC of the target transmission (312); and if no switching has been commanded, actuate the switching valve (120) from the open position to the closed position if the target ROC (210) is less than the maximum ROC of the target transmission (312).

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