Diagnostic device for a switching control actuator

Abstract

Diagnostic device for a shift control unit of a continuously variable transmission, comprising the following: - a variator (110, 120, 130) for continuously changing a gear ratio from a predetermined maximum gear ratio to a predetermined minimum gear ratio; - a chamber (112) for reducing the transmission ratio of the variator (110, 120, 130) by filling it with hydraulic fluid, and increasing the transmission ratio of the variator (110, 120, 130) by draining the hydraulic fluid; - a switching control valve (140) that switches between a filling state in which the hydraulic fluid supplied by an oil pump is filled into the chamber (112) and a non-filling state in which the filling of the hydraulic fluid into the chamber (112) is interrupted; - a downshift control valve (150) that switches between a drain state in which the hydraulic fluid is drained from the chamber (112) and a non-drain state in which the draining of the hydraulic fluid from the chamber (112) is interrupted; - a safety valve (160) to interrupt the draining of the hydraulic fluid from the chamber (112) when the up-shift control valve (140) is in the filling state, regardless of the state of the down-shift control valve (150), in particular regardless of the draining state of the down-shift control valve (150), and to allow the down-shift control valve (150) to drain the hydraulic fluid when the up-shift control valve (140) is in the non-filling state; - a high-speed control element for driving the high-speed control valve (140) for switching between the filled state and the non-filled state; - a downshift control element for driving the downshift control valve (150) for switching between the draining state and the non-draining state; - an actual gear ratio detection device for recording an actual gear ratio of the variator (110, 120, 130); and - a switching control device for controlling the upshifting control element and the downshifting control element, so that the actual gear ratio approximates the target gear ratio, - wherein, when the switching control device controls the downshift control element in such a way that the downshift control valve (150) enters the drain state, and a state in which the actual transmission ratio is essentially maintained at the smallest transmission ratio persists for a predetermined period of time or longer, the switching control device determines that the upshift control element is maintained in the filling state.

Description

Technical area

[0001] The present invention relates to a diagnostic device for a shift control actuator of a continuously variable transmission (CVT) provided in a vehicle such as an automobile, and more particularly to a diagnostic device capable of appropriately detecting a steady-on state of an upshift control device or a downshift control device. Background of the invention

[0002] Continuously variable transmissions (CVTs), which are installed in vehicles such as automobiles and change a gear ratio of an output speed of, for example, an engine, are provided with a variator (shifting mechanism) that can continuously change the gear ratio through hydraulic control. In a known example of such a variator, a power transmission element, such as a chain or a metal belt, bridges a first pulley (drive-side pulley) and a second pulley (driven-side pulley) whose rotational axes are parallel to each other, and the gear ratio changes when the effective diameter of the respective pulleys is hydraulically changed.

[0003] In such a variator, for example, it is known that the variator is configured to perform an upshift by filling a chamber provided in the first pulley with a hydraulic fluid and to perform a downshift by discharging the hydraulic fluid from the chamber, and is provided with an upshift control valve for switching a filling state of the hydraulic fluid to the chamber and a downshift control valve for switching a discharging state of the hydraulic fluid from the chamber.

[0004] The upshift control valve and the downshift control valve are driven by respective shift control actuators, such as electromagnets.

[0005] Thus, in the continuously variable transmission which changes the gear ratio using the upshift and downshift actuators, proper diagnosis of the normal state and abnormal state of each actuator is required.

[0006] As a technique relevant to such a diagnosis of the shift control actuator, for example, Japanese Unexamined Patent Application Publication JP 2006-248371 A discloses that when an upshift or a downshift of the continuously variable transmission is not properly performed, the upshift and downshift solenoids are turned on simultaneously, and it is determined which solenoid has failed based on the transitions of the gear ratios at that time.

[0007] However, with the conventional technique described above, it takes a long time to achieve fault diagnosis because a specific state in which both the upshift and downshift solenoids are turned on must be set after first determining that the shift control is not being performed properly. Furthermore, for example, in the case where the downshift solenoid enters a permanently on state, the hydraulic fluid is discharged at maximum speed when the upshift solenoid is turned off.

[0008] However, when the gear ratio becomes higher than a target gear ratio, the upshift solenoid is turned on through feedback control, allowing hydraulic fluid to fill the chamber. Therefore, a control oscillation occurs, in which an overshoot is repeated, but the feedback control itself, which brings the actual gear ratio close to the target gear ratio, is still possible, so that a fault detection may not be performed.

[0009] From US 4 698 764 A a diagnostic device for a CVT is known, the gear ratio and / or the rate of change of the gear ratio is controlled by a shift control device controlled by command signals from a control system.The diagnostic device that checks whether the gear ratio is normally controlled comprises: a detection device for detecting an actual gear ratio and / or an actual change rate of the gear ratio; a memory that stores data for determining normal ranges of the gear ratio and / or normal ranges of the change rate of the gear ratio, the normal ranges corresponding to shift conditions of the transmission set by the shift control device according to the command signals; and a judgment device for selecting one of the normal ranges of the gear ratio and / or one of the normal ranges of the change rate of the gear ratio based on the command signals.The assessment device checks whether the detected actual speed ratio and / or the detected actual rate of change of the speed ratio fall within the selected normal ranges.

[0010] From US 2009 / 0 264 231 A1, a hydraulic control system of a vehicle drivetrain is known, which has a belt-type CVT and a hydraulic lock-up clutch. The control system comprises the following: a line pressure control valve; first and second control valves; first, second, and third electromagnetic valves; and a fail-safe valve. The fail-safe valve is switched to a fail-safe position, in which line pressure is supplied to either a drive pulley or a driven pulley when a rapid deceleration condition is expected to occur in the CVT. Furthermore, the fail-safe valve is switched to a normal position, in which hydraulic pressure output from the first control valve is supplied to either the drive pulley or the driven pulley during times other than those mentioned above.The fail-safe valve is switched by a combination of hydraulic pressure controlled by the second electromagnetic valve and hydraulic pressure controlled by the third electromagnetic valve.

[0011] From US 2006 / 0 169 036 A1, a failure determination system for a CVT is known, comprising: gear ratio detection means for detecting a gear ratio between a drive pulley and a driven pulley; vehicle speed detection means for detecting a vehicle speed of the vehicle; and failure determination means for determining a failure of at least one of the drive-side control valve and the driven-side control valve based on the following values: the gear ratio detected either at a time during the vehicle stop or at a time immediately before the vehicle stop; the gear ratio detected after a restart of the vehicle after the stop; and the detected vehicle speed. Brief description of the invention

[0012] The present invention has been conceived in consideration of the above-described situations and provides a diagnostic device for a shift control device which can appropriately detect a permanent ON state of an upshift control device or a downshift control device.

[0013] One aspect of the invention provides a diagnostic device for a shift control actuator of a continuously variable transmission, the diagnostic device comprising: a variator; a chamber; an upshift control valve; a downshift control valve; a safety valve; an upshift control member; a downshift control member; an actual gear ratio detecting device; and a shift control device. The variator continuously changes a gear ratio from a predetermined maximum gear ratio to a predetermined minimum gear ratio.

[0014] The chamber reduces the variator's gear ratio by filling it with hydraulic fluid and increases the variator's gear ratio by draining the hydraulic fluid. The upshift control valve switches between a filled state, in which hydraulic fluid supplied by an oil pump fills the chamber, and a non-filled state, in which filling of the chamber with hydraulic fluid is interrupted.

[0015] The downshift control valve switches between a drain state in which the hydraulic fluid is drained from the chamber and a non-drain state in which the drain of the hydraulic fluid from the chamber is interrupted. The safety valve interrupts the drain of the hydraulic fluid from the chamber when the upshift control valve is in the filled state, regardless of the state of the downshift control valve, and allows the downshift control valve to drain hydraulic fluid when the upshift control valve is in the non-filled state. The upshift control member controls the upshift control valve to switch between the filled state and the non-filled state.

[0016] The downshift control element controls the downshift control valve to switch between the release state and the non-release state. The actual gear ratio detection device detects the actual gear ratio of the variator. The shift control element controls the upshift control element and the downshift control element to bring the actual gear ratio closer to a target gear ratio.

[0017] When the shift control device controls the downshift control member such that the downshift control valve enters the discharge state, and a state in which the actual gear ratio is maintained substantially at the smallest gear ratio continues for a predetermined period of time or longer, the shift control device determines that the upshift control member is maintained in the fill state.

[0018] It should be noted that the term "gear ratio," as used herein and in the claims, defines a ratio of an output speed of the variator to an input speed of the variator (a speed reduction ratio). Further, it should be noted that the term "downshift," as used herein and in the claims, defines an increasing change in the gear ratio, and the term "upshift," as used herein and in the claims, defines a decreasing change in the gear ratio.

[0019] When the transmission control device controls the upshift control member such that the upshift control valve enters the fill state, and an event in which the actual gear ratio increases is detected with a predetermined frequency or more often, the shift control device may determine that the downshift control member is maintained in a drain state.

[0020] Another aspect of the invention provides a diagnostic device for a shift control actuator of a continuously variable transmission, the diagnostic device comprising: a variator; a chamber; an upshift control valve; a downshift control valve; a safety valve; an upshift control member; a downshift control member; an actual gear ratio detecting device; and a shift control device. The variator continuously changes a gear ratio from a predetermined maximum gear ratio to a predetermined minimum gear ratio.

[0021] The chamber reduces the variator's gear ratio by filling it with hydraulic fluid and increases the variator's gear ratio by draining the hydraulic fluid. The upshift control valve switches between a filled state, in which hydraulic fluid supplied by an oil pump fills the chamber, and a non-filled state, in which filling of the chamber with hydraulic fluid is interrupted.

[0022] The downshift control valve switches between a drain state, in which the hydraulic fluid is drained from the chamber, and a non-drain state, in which the drain of the hydraulic fluid from the chamber is stopped. The safety valve stops the drain of the hydraulic fluid from the chamber when the upshift control valve is in the filled state, regardless of the state of the downshift control valve, and allows the downshift control valve to drain hydraulic fluid when the upshift control valve is in the non-filled state.

[0023] The upshift control element controls the upshift control valve to switch between the filled and unfilled states. The downshift control element controls the downshift control valve to switch between the drained and undrained states. The actual gear ratio detection device detects an actual gear ratio of the variator. The shift control device controls the upshift control element and the downshift control element so that the actual gear ratio approaches a target gear ratio.

[0024] When the shift control device controls the upshift control member such that the upshift control valve enters the filling state, and the event in which the actual gear ratio increases is detected at a predetermined frequency or more often, the shift control device determines that the downshift control member is maintained in the discharge state.

[0025] The downshift control device may have a function of continuously or multiplying the discharge rate of the hydraulic fluid from the chamber according to an increase in a controlled variable. The shift control device may determine that the upshift control device is maintained in the filled state only when the controlled variable of the downshift control device is at or above a predetermined value.

[0026] The upshift control device may have a function of continuously or multiplying the filling rate of the hydraulic fluid into the chamber according to an increase in a controlled variable. The shift control device may determine that the downshift control device is maintained in the discharge state only when the controlled variable of the upshift control device is at or above a predetermined value. Brief description of the drawings

[0027] The present invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the same reference numerals designate the same elements. Fig. 1 is a schematic diagram illustrating a configuration of a diagnostic device for a shift control actuator and a continuously variable transmission according to an embodiment of the present invention, and illustrating an upshift state under normal conditions; Fig. 2 is a schematic diagram illustrating a configuration of a diagnostic device for a shift control actuator and a continuously variable transmission according to the embodiment of the present invention, and illustrating a downshift state under normal conditions; Fig. 3 is a flowchart illustrating a steady-on diagnosis of an upshift control solenoid in the shift control actuator diagnostic device according to the embodiment; Fig. 4 is a schematic diagram illustrating the configuration of the shift control actuator diagnostic device and the continuously variable transmission according to the embodiment of the present invention, and illustrating a permanently ON state of the upshift control solenoid switch; Fig. 5 is a flowchart illustrating a steady-on diagnosis of a downshift control solenoid in the shift control actuator diagnostic device according to the embodiment of the present invention; Fig. 6 is a schematic diagram illustrating the configuration of the shift control actuator diagnostic device and the continuously variable transmission according to the embodiment of the present invention, and illustrating a state in which a shift control device instructs a downshift at the time of a permanently ON state of a downshift control solenoid; and Fig. 7 is a schematic diagram illustrating the configuration of the shift control actuator diagnostic device and the continuously variable transmission according to the embodiment of the present invention, and illustrating a state in which the shift control device instructs an upshift at the time of a steady-on state of the downshift control solenoid switch. Detailed description

[0028] A diagnostic device for a shift control actuator according to the present invention is capable of appropriately detecting a permanently on state of an upshift control device or a downshift control device. The diagnostic device detects the permanently on state of the upshift control solenoid when a gear ratio is maintained at a minimum gear ratio (overdrive: OD) even though a downshift control solenoid is turned on.

[0029] The diagnostic device also detects a continuous off condition of the downshift control solenoid when a gear ratio increase (downshift) event occurs at a predetermined frequency or more frequently even though the upshift control solenoid is on. Design

[0030] An embodiment of the diagnostic device for a shift control actuator (hereinafter referred to as "the diagnostic device") according to the present invention will be described below. The diagnostic device according to this embodiment diagnoses a fault in the permanently ON state of an upshift control device and a downshift control device of a continuously variable transmission (CVT) installed in a vehicle such as an automobile.

[0031] Fig. 1 is a schematic diagram showing a configuration of the diagnostic device and the continuously variable transmission according to this embodiment, and showing an upshift state under normal conditions. Fig. 2 is a schematic diagram showing the configuration of the diagnostic device and the continuously variable transmission according to this embodiment, and showing a downshift state under normal conditions.

[0032] The continuously variable transmission 100 includes a first pulley 110, a second pulley 120, a chain 130, an upshift control valve 140, a downshift control valve 150, a safety valve 160, and a transmission control unit 200.

[0033] The first pulley 110 is a rotating body and receives a rotational drive from a vehicle engine. The first pulley 110 is constructed such that a pair of conical discs, between which the chain 130 is clamped, are arranged opposite each other. The first pulley 110 can change the effective diameter around which the chain 130 is wound by bringing the conical discs closer to or further apart in the axial direction. A rotation sensor 111 for detecting a rotational speed is provided on the first pulley 110.

[0034] A chamber 112 is provided on the first pulley 110. The chamber 112 contains hydraulic fluid to reduce the distance between the conical discs of the first pulley 110, thereby increasing the effective diameter (upshifting). On the other hand, the hydraulic fluid is drained from the chamber 112 to increase the distance between the conical discs, thereby decreasing the effective diameter (downshifting).

[0035] The second pulley 120 is a rotating body connected to the drive wheels of a vehicle via a powershift mechanism, such as a transmission, and rotates about a rotational axis parallel to the first pulley 110. The second pulley 120 is constructed such that a pair of tapered discs, which clamp the chain 130 between them, are arranged opposite each other. The second pulley 120 can change its effective diameter, around which the chain 130 is wound, by bringing the tapered discs closer to or further apart in the axial direction.

[0036] The second pulley 120 reduces its effective diameter in a cooperative manner with an increase in the effective diameter of the first pulley 110, and increases its effective diameter in a cooperative manner with a decrease in the effective diameter of the first pulley 110. A rotation sensor 121 for detecting a rotational speed is provided on the second pulley 120.

[0037] The chain 130 is wound around the first pulley 110 and the second pulley 120 to transmit power between these pulleys. The first pulley 110, the second pulley 120, and the chain 130 cooperate to form a variator (shifting mechanism) of the continuously variable transmission 100, which can continuously change a gear ratio.

[0038] After an oil pump (not shown) pressurizes and discharges hydraulic fluid, the upshift control valve 140 switches between filling and cutting off the hydraulic fluid to the chamber 112, with the hydraulic fluid regulated to a predetermined secondary pressure by a hydraulic regulator. The upshift control valve 140 is operated by an upshift control solenoid (not shown).

[0039] The upshift control solenoid is turned on to fill the chamber 112 with hydraulic fluid, and on the other hand, the upshift control solenoid is turned off to stop the filling of the chamber 112 with hydraulic fluid. The upshift control solenoid essentially continuously increases a filling rate of the hydraulic fluid according to an increase in the duty cycle of the drive current (0% to 100%).

[0040] A downshift control valve 150 switches between draining and interrupting the hydraulic fluid within chamber 112. The downshift control valve 150 is driven by a downshift control solenoid (not shown). The downshift control solenoid is energized to drain the hydraulic fluid from chamber 112.

[0041] On the other hand, the downshift control solenoid is turned off to stop the discharge of hydraulic fluid from chamber 112. The downshift control solenoid essentially continuously increases the discharge rate of the hydraulic fluid according to an increase in the duty cycle of the drive current (0% to 100%).

[0042] A safety valve 160 is provided on a hydraulic fluid discharge passage extending from the first pulley 110 to the downshift control valve 150. The safety valve 160 interrupts the hydraulic fluid discharge line to stop the discharge of the hydraulic fluid regardless of a state of the downshift control valve 150 when the upshift control valve 140 is in an open state (filled state) and sets the duty ratio of the upshift control member above the predetermined value.

[0043] On the other hand, when the upshift control valve 140 is in a closed state (filling state interrupted), the safety valve 160 goes into an open state by the biasing force of a spring, and in this state, the downshift control valve 150 is opened to discharge the hydraulic fluid from the chamber 112.

[0044] The transmission control unit 200 comprehensively controls the continuously variable transmission 100 and its ancillary components. The transmission control unit 200 includes an information processor, such as a CPU, a memory, such as a RAM or ROM, an input / output interface, and a bus connecting these components.

[0045] The transmission control unit 200 further includes a target gear ratio calculator 210, an actual gear ratio calculator 220, and a feedback controller 230. The target gear ratio calculator 210 calculates a target gear ratio of the continuously variable transmission 100 using a predefined map based on a driving condition of the vehicle and / or a drive torque requested by an operator of the vehicle.

[0046] The actual gear ratio calculator 22 calculates an actual gear ratio of the continuously variable transmission 100 (actual gear ratio = rotational speed of the second pulley / rotational speed of the first pulley) based on the rotational speed of the first pulley 110 detected by the rotation sensor 111 and the rotational speed of the second pulley 120 detected by the rotation sensor 121.

[0047] The feedback controller 230 performs feedback control of the upshift control solenoid and the downshift control solenoid based on a difference between a target gear ratio calculated by the target gear ratio calculator 210 and the actual gear ratio calculated by the actual gear ratio calculator 22, so that the actual gear ratio approaches the target gear ratio.

[0048] How Fig. As shown in Figure 1, when the actual gear ratio is higher than the target gear ratio, the feedback controller 230 issues an on command to the upshift control solenoid valve, while issuing an off command to the downshift control solenoid valve. The feedback controller 230 sets the duty ratio of the upshift control solenoid valve higher when the difference between the target gear ratio and the actual gear ratio is large, thus requiring a rapid change in the gear ratio.

[0049] Accordingly, the upshift control valve 140 is opened, and the chamber 112 is filled with hydraulic fluid. Furthermore, the downshift control valve 150 and the safety valve 160 are closed, and thus the hydraulic fluid is not drained from the chamber 112. As a result, the effective diameter of the first pulley 110 increases, while the effective diameter of the second pulley 120 decreases, so that the gear ratio of the continuously variable transmission 100 is reduced (upshift).

[0050] How Fig. As shown in Figure 2, when the actual gear ratio is lower than the target gear ratio, the feedback controller 230 issues an off command to the upshift control solenoid valve, while issuing an on command to the downshift control solenoid valve. The feedback controller 230 sets the duty ratio of the downshift control solenoid valve higher when the difference between the target gear ratio and the actual gear ratio is large, thus requiring a rapid change in the gear ratio.

[0051] At this time, the upshift control valve 140 is closed, the safety valve 160 is opened, the downshift control valve 150 is opened, and the hydraulic fluid within the chamber 112 is discharged at a rate corresponding to the duty cycle of the downshift control solenoid. As a result, the effective diameter of the first pulley 110 decreases while the effective diameter of the second pulley 120 increases, so that the gear ratio of the continuously variable transmission 100 increases (downshift).

[0052] The transmission control unit 200 also functions as a diagnostic device for diagnosing failures of the upshift control solenoid and the downshift control solenoid in the continuously variable transmission 100. When the transmission control unit 200 commands a duty ratio above a predetermined value for the upshift control solenoid, but an upshift is not performed, the transmission control unit 200 determines a permanently off state of the upshift control solenoid.

[0053] On the other hand, when the transmission control unit 200 commands the duty ratio over the predetermined value for the downshift control solenoid, but a downshift is not executed, the transmission control unit 200 determines the permanent off state of the downshift control solenoid.

[0054] In addition, the transmission control unit 200 diagnoses the continuous on state of the upshift control solenoid and the downshift control solenoid (maintained in an energized state even though no current is applied to them) as described below.

[0055] Fig. Figure 3 is a flowchart illustrating the diagnosis of a permanently ON state of an upshift control solenoid in the diagnostic device of this embodiment. The diagnosis will be described in sequence step by step below. Step S01: Diagnosis by performing a condition determination

[0056] The transmission control unit 200 determines whether all of the conditions described below are met. If all conditions are met, the transmission control unit 200 proceeds to step S02, and if at least one of the conditions is not met, the transmission control unit 200 proceeds to step S03. These conditions are determined based on the fact that diagnosis is not performed in a state where an operating state of the transmission is in transition to prevent misdiagnosis. The conditions are as follows: a) A state in which the duty ratio of the downshift control solenoid switch is over a predetermined value (for example, 30%), continues for a predetermined period of time (for example, 0.1 s) or longer. b) The duty cycle of the upshift control solenoid is 0%. c) The engine speed is at a predetermined value (for example 1000 min -1 ) or above. d) The speed of the second pulley is at a predetermined value (for example 500 min -1 ) or above. e) An actual secondary pressure is at a predetermined value (e.g. 0.6 MPa) or above. f) A state in which the duty ratio of a pressure control solenoid valve of a lock-up clutch is above a predetermined value (for example, 90%) or at 0%, continues for a predetermined period of time (for example, 0.1 s) or longer. g) A state in which the current value of a pressure control solenoid valve of an FR clutch is at a predetermined value (for example, 0.7 A) or below, continues for a predetermined period of time (for example, 0.1 s) or longer. Step S02: Diagnostic execution conditions met

[0057] The transmission control unit 200 proceeds to step S04 assuming that the execution conditions of the upshift control solenoid switch continuous ON state diagnosis are satisfied. Step S03: Diagnostic execution conditions not met

[0058] The transmission control unit 200 ends the series of processes (return) assuming that the execution conditions of the upshift control solenoid switch continuous ON state diagnosis are not satisfied. Step S04: Determination of diagnostic conditions

[0059] The transmission control unit 200 determines whether all of the conditions described below are met. If all of the conditions are met, the transmission control unit 200 proceeds to step S05, and if at least one of the conditions is not met, the series of processes is terminated (return). a) A change in a filtered gear ratio is at a predetermined value (for example -0.05 [1 / S]) or above. b) The change in the filtered gear ratio is at a predetermined value (for example 0.05 [1 / S]) or below.

[0060] It should be noted that the filter here is a low-pass filter aimed at noise removal, and the change in the filtered gear ratio can be calculated, for example, using equation 1. The above conditions a) and b) mean that the gear ratio has not been significantly changed. Change in the filtered gear ratio [n] = predetermined value (0.01) × change in the gear ratio [n] + 1 (1 − predetermined value (0.01)) × change in the gear ratio [n − 1] c) The actual gear ratio is at a predetermined value (e.g. 0.5) or below.

[0061] The predetermined value is set to a value substantially equal to the minimum gear ratio (OD gear ratio) of the continuously variable transmission 100. d) A state in which the duty ratio of the downshift control solenoid switch is over a predetermined value (for example, 80%), continues for a predetermined period of time (for example, 0.1 s) or longer. Step S05: Setting an error detection flag

[0062] The transmission control unit 200 sets a continuous ON-detected error flag of the upshift control solenoid and ends the series of processes (return).

[0063] Fig. Figure 4 is a schematic diagram showing a configuration of the diagnostic device and the continuously variable transmission according to this embodiment, and illustrating the permanently ON state of the upshift control solenoid. Fig. 4, when the transmission control unit 200 issues the on command to the downshift control solenoid and the off command to the upshift control solenoid to perform a downshift, but the upshift control solenoid is in the permanently on state, the chamber 112 is continuously filled with the hydraulic fluid, and the safety valve 160 is also closed, so that the discharge of the hydraulic fluid from the chamber 112 is interrupted.

[0064] As a result, the gear ratio of the continuously variable transmission 100 is maintained at substantially the lowest gear ratio. Thus, as described above, a fault is diagnosed when the duty ratio of the downshift control solenoid is at or above the predetermined value, but the state in which the filtered gear ratio is substantially unchanged is maintained for the predetermined period of time, so that the continuous on state of the upshift control solenoid can be appropriately determined.

[0065] Fig. Figure 5 is a flowchart illustrating a diagnosis of the permanently ON state of a downshift control solenoid in the diagnostic device according to this embodiment. The diagnosis is described in sequence step by step below. Step S 11: Diagnosis by performing a condition determination

[0066] The transmission control unit 200 determines whether all of the conditions described below are met. If all conditions are met, the transmission control unit 200 proceeds to step S12. Conversely, if at least one of the conditions is not met, the transmission control unit 200 proceeds to step S13. These conditions are determined based on the fact that diagnosis is not performed in a state where an operating state of the transmission is in transition, in order to prevent misdiagnosis.

[0067] The conditions are as follows: a) A state in which the duty ratio of the upshift control solenoid switch is at a predetermined value (for example, 10%) or more, continues for a predetermined period of time (for example, 0.1 s) or longer. b) The duty cycle of the downshift control solenoid is 0%. c) The actual gear ratio lies within a predetermined range (average gear ratio) in which a control oscillation can occur (for example in the range from 0.5 to 2.3). d) The engine speed is set to a predetermined value (for example 1000 min -1 ) or above. e) The speed of the second pulley is set to a predetermined value (for example 500 min -1 ) or above. f) The actual secondary pressure is at a predetermined value (e.g. 0.6 MPa) or above. g) A state in which the duty ratio of a pressure control solenoid valve of a lock-up clutch is at a predetermined value (for example, 90%) or more or at 0% continues for a predetermined period of time (for example, 0.1 s) or longer. h) A state in which the current value of a pressure control solenoid valve of an FR clutch is at a predetermined value (for example, 0.7 A) or below, continues for a predetermined period of time (for example, 0.1 s) or longer. Step S12: Diagnostic execution conditions met

[0068] The transmission control unit 200 proceeds to step S14 assuming that the execution conditions of the downshift control solenoid switch continuous ON state diagnosis are satisfied. Step S13: Diagnostic execution conditions not met

[0069] The transmission control unit 200 ends the series of processes (return) assuming that the execution conditions of the continuous ON-state diagnosis of the downshift control solenoid are not satisfied. Step S14: Determination of error detection

[0070] The transmission control unit 200 determines whether all of the conditions described below are met. If all of the conditions are met, the transmission control unit 200 proceeds to step S15. Conversely, if at least one of the conditions is not met, the transmission control unit 200 proceeds to step S16. a) The change in the filtered gear ratio is at or above a predetermined value (e.g., -0.05 [1 / S]). Here, the change in the filtered gear ratio is the same as the change described in Equation 1 above. b) A state in which the duty ratio of the upshift control solenoid switch is at a predetermined value (for example, 50%) or above, continues for a predetermined period of time (for example, 0.1 s) or longer. Step S15: Setting an error detection flag

[0071] The transmission control unit 200 sets an error detection flag and then proceeds to step S17. Step S16: Clear the error detection flag

[0072] The transmission control unit 200 clears the error detection flag and then ends the series of processes (return). Step S17: Detecting a change in the error detection flag

[0073] The transmission control unit 200 proceeds to step S18 if the error detection flag is changed from a flag-cleared state to a flag-set state in the preceding step S15. On the other hand, the transmission control unit 200 ends the series of processes (return) if the error detection flag was in the set state before the preceding step S15 and the error detection flag remains unchanged in the set state. Step S18: Increment the error counter

[0074] The transmission control unit 200 increments a count value of an error counter for counting the number of changes in the error detected flag, which is changed from the cleared state to the set state in step S17. The transmission control unit 200 then proceeds to step S19. Step S19: Determine the error counter value

[0075] The transmission control unit 200 determines whether the count value of the error counter reaches a predetermined value (e.g., 10 times) or more within a 10-second period. If the count value is the predetermined value or greater, the transmission control unit 200 proceeds to step S20; on the other hand, if it is below a predetermined value, the transmission control unit 200 proceeds to step S21. Step S20: Setting an error detected flag

[0076] The transmission control unit 200 sets the continuous ON state error detected flag of the downshift control solenoid and then ends the series of processes (return). Step S21: Clear the error counter

[0077] The transmission control unit 200 clears the count value of the error counter and then ends the series of processes (return).

[0078] Fig. 6 is a schematic diagram illustrating the configuration of the diagnostic device and the continuously variable transmission according to this embodiment, and illustrating a state in which the transmission control unit instructs a downshift during a permanently ON state of the downshift control solenoid.

[0079] How Fig. 6, when the transmission control unit 200 outputs an ON command to the downshift control solenoid and an OFF command to the upshift control solenoid to perform a downshift, the downshift control valve 150 is in a fully open state regardless of the duty ratio of the downshift control solenoid, and therefore the hydraulic fluid within the chamber 112 is discharged at the maximum speed, and a downshift is performed at a high speed.

[0080] As a result, an overshoot occurs in which the actual gear ratio of the continuously variable transmission 100 exceeds the target gear ratio.

[0081] Fig. 7 is a schematic diagram illustrating the configuration of the diagnostic device and the continuously variable transmission according to this embodiment, and illustrating a state in which the transmission control unit 200 instructs an upshift during a permanently ON state of the downshift control solenoid.

[0082] How Fig. As shown in FIG. 7, when the shift control unit 200 issues an on command to the upshift control solenoid and an off command to the downshift control solenoid to perform an upshift, the safety valve 160 is closed in conjunction with the opening of the upshift control valve 140. Accordingly, the filling of the hydraulic fluid into the chamber 112 can be properly performed even when the downshift control valve 150 is in a fully open state.

[0083] Then, when the actual gear ratio of the continuously variable transmission 100 is shifted up until it becomes smaller than the target gear ratio, the transmission control unit 200 again instructs a downshift through the feedback control and then returns to the Fig. 6. After that, the states in Fig. 6 and Fig. 7 is repeated frequently, so that a control oscillation occurs.

[0084] Thus, as described above, by diagnosing a failure when the duty ratio of the upshift control solenoid is over a predetermined value but in the state where downshifts have occurred at a predetermined frequency or more, the continuous on state of the downshift control solenoid can be appropriately determined.

[0085] As described above, according to this configuration, the following effects can be achieved. (1) The continuous ON state of the upshift control solenoid may be appropriately determined based on whether the transmission control unit 200 drives the downshift control solenoid so that the downshift control valve 150 enters the vent state, and a state in which the actual gear ratio is substantially maintained at a smallest gear ratio continues for a predetermined period of time or longer. (2) It may be appropriately determined that the downshift control solenoid is maintained in the discharge state based on whether the transmission control unit 200 controls the upshift control solenoid so that the upshift control valve 240 enters the fill state and an event in which the actual gear ratio is increased is detected at a predetermined frequency or more. (3) Erroneous detections can be prevented to improve the accuracy of detection by detecting the continuous on state of the upshift control solenoid switch only when the duty ratio of the upshift control solenoid switch is over the predetermined value, and by detecting the continuous on state of the downshift control solenoid switch only when the duty ratio of the upshift control solenoid switch is over the predetermined value. Modifications

[0086] The present invention is not limited to the embodiment described above. Various modifications and variations can be made, which are also within the technical scope of the present invention. For example, the continuously variable transmission of the embodiment described above is a chain-type continuously variable transmission that uses a pair of variable pulleys and a chain as a variator.

[0087] Alternatively, the present invention can also be applied to continuously variable transmissions with a variator of other types, such as belt-type and toroidal-type. Furthermore, the continuously variable transmission of the above-described embodiment uses a magnetic switch as the shift control actuator. Alternatively, it may also use, for example, a stepper motor. The various types of numerical parameters are merely examples and can be changed as appropriate.

[0088] The foregoing description describes specific embodiments of the present invention. However, those skilled in the art will recognize that various adaptations and modifications may be made without departing from the scope of the present invention as set forth in the following claims. Accordingly, the description and figures are to be regarded in an illustrative rather than a limiting sense, and all such modifications are intended to be included within the scope of the present invention.

[0089] The advantages, beneficial effects, solutions to problems, and any elements that may cause the occurrence or prominence of a beneficial effect, advantage, or solution are not to be construed as critical, required, or essential features or elements of any or all of the claims. The invention is defined solely by the appended claims, including any amendments made during the probable course of this application, and all equivalents to those claims as published. List of reference symbols 100 continuously variable transmission 110 First pulley 111 Rotation sensor 112 Chamber 120 Second pulley 121 rotation sensor 130 chain 140 Upshift control valve 150 Downshift control valve 160 Safety valve 200 transmission control unit 210 Target gear ratio calculator 220 Actual Gear Ratio Calculator 230 Feedback control

Claims

[1] Diagnostic device for a shift control element of a continuously variable transmission, comprising: - a variator (110, 120, 130) for continuously changing a gear ratio from a predetermined highest gear ratio to a predetermined lowest gear ratio; - a chamber (112) for reducing the gear ratio of the variator (110, 120, 130) by filling it with hydraulic fluid and increasing the gear ratio of the variator (110, 120, 130) by draining the hydraulic fluid; - an upshift control valve (140) which switches between a filling state in which the hydraulic fluid supplied by an oil pump is filled into the chamber (112) and a non-filling state in which the filling of the hydraulic fluid into the chamber (112) is interrupted; - a downshift control valve (150) that switches between a drain state in which the hydraulic fluid is drained from the chamber (112) and a non-drain state in which the drain of the hydraulic fluid from the chamber (112) is interrupted; - a safety valve (160) for interrupting the discharge of hydraulic fluid from the chamber (112) when the upshift control valve (140) is in the filled state, regardless of the state of the downshift control valve (150), in particular regardless of the discharge state of the downshift control valve (150), and for allowing the downshift control valve (150) to discharge the hydraulic fluid when the upshift control valve (140) is in the non-filled state; - an upshift control member for driving the upshift control valve (140) to switch between the filling state and the non-filling state; - a downshift control member for driving the downshift control valve (150) to switch between the discharge state and the non-discharge state; - an actual gear ratio detecting device for detecting an actual gear ratio of the variator (110, 120, 130); and - a shift control device for controlling the upshift control element and the downshift control element so that the actual gear ratio approaches the target gear ratio, - wherein, when the shift control means controls the downshift control member so that the downshift control valve (150) enters the discharge state, and a state in which the actual gear ratio is maintained substantially at the smallest gear ratio continues for a predetermined period of time or longer, the shift control means determines that the upshift control member is maintained in the fill state. [2] A diagnostic device according to claim 1, wherein when the shift control means controls the upshift control member to cause the upshift control valve (140) to enter the fill state, and an event in which the actual gear ratio increases is detected at a predetermined frequency or more, the shift control means determines that the downshift control member is maintained in the discharge state. [3] Diagnostic device for a shift control element of a continuously variable transmission, comprising: - a variator (110, 120, 130) for continuously changing a gear ratio from a predetermined highest gear ratio to a predetermined lowest gear ratio; - a chamber (112) for reducing the gear ratio of the variator (110, 120, 130) by filling it with hydraulic fluid and increasing the gear ratio of the variator (110, 120, 130) by draining the hydraulic fluid; - an upshift control valve (140) which switches between a filling state in which the hydraulic fluid supplied by an oil pump is filled into the chamber (112) and a non-filling state in which the filling of the hydraulic fluid into the chamber (112) is interrupted; - a downshift control valve (150) that switches between a drain state in which the hydraulic fluid is drained from the chamber (112) and a non-drain state in which the drain of the hydraulic fluid from the chamber (112) is interrupted; - a safety valve (160) for interrupting the discharge of hydraulic fluid from the chamber (112) when the upshift control valve (140) is in the filled state, regardless of the state of the downshift control valve (150), in particular regardless of the discharge state of the downshift control valve (150), and for allowing the downshift control valve (150) to discharge the hydraulic fluid when the upshift control valve (140) is in the non-filled state; - an upshift control member for driving the upshift control valve (140) to switch between the filling state and the non-filling state; - a downshift control member for driving the downshift control valve (150) to switch between the discharge state and the non-discharge state; - an actual gear ratio detecting device for detecting an actual gear ratio of the variator (110, 120, 130); and - a shift control device for controlling the upshift control member and the downshift control member so that the actual gear ratio approaches the target gear ratio, wherein when the shift control device controls the upshift control member to cause the upshift control valve (140) to enter the fill state, and an event in which the actual gear ratio increases is detected at a predetermined frequency or more often, the shift control device determines that the downshift control member is maintained in the drain state. [4] Diagnostic device according to one of claims 1 to 3, wherein the downshift control member has a function of varying a discharge rate of the hydraulic fluid from the chamber (112) according to an increase in a controlled variable thereof continuously or in a plurality of steps, and wherein the shift control means determines that the upshift control member is maintained in the fill state only when the controlled variable of the downshift control member is at or above a predetermined value. [5] Diagnostic device according to one of claims 1 to 4, wherein the upshift control member has a function of varying a filling rate of the hydraulic fluid into the chamber (112) according to an increase in a controlled variable thereof continuously or in a plurality of steps, and wherein the shift control means determines that the downshift control member is maintained in the bleed state only when the controlled variable of the upshift control member is at or above a predetermined value.

Images