Automatic transmission shift quality improved via selective use of closed-loop pressure feedback control

[0050] Reference will now be made to the accompanying drawings, wherein the drawings are presented for purposes of illustrating certain exemplary embodiments only and not for the purpose of limiting the same, figure 1An exemplary clutch control system employing a regulator valve in accordance with the present invention is schematically shown. The clutch control system 200 includes a regulator valve 210 , a pressure switch 240 , and hydraulic lines 270 , 272 , 274 , 276 , 278 and 280 . Regulator valve 210 selectively controls the flow of pressurized hydraulic oil in and out of the hydraulically actuated clutch through movement of a selection mechanism (in the exemplary embodiment, spool valve plunger 220 ) within the regulator valve. The plunger 220 is selectively actuated by the first end 222 of the plunger and the second end 224 of the plunger, and the balance of forces determines the displacement position of the plunger within the regulating valve. The plunger 220 includes a plunger detail (or plunger detail) 226 (including holes, grooves, passages, or other features) formed thereon to allow hydraulic oil to flow at various points that connect the hydraulic lines to the regulator valve 210 . Boot selectively between ports. The position of the plunger 220 within the regulator valve 210 corresponds to the clutch conditions described above, which position selectively aligns the plunger detail 226 with the hydraulic lines that perform the intended clutch function. exist figure 1 In the exemplary system of , the plunger position to the extreme right corresponds to a full supply condition in which hydraulic pressure from main pressure line 272 is directed through plunger detail 226 to clutch supply line 276 . The hydraulic pressure from main pressure line 272 may be referred to as P LINE. Similarly, the plunger position to the extreme left corresponds to a drain condition in which hydraulic oil within the clutch is permitted to exit the clutch from clutch supply line 276, pass through plunger detail 226 to flow through drain line 274, and into the hydraulic control system return line . The selection of the position of the plunger 220 is accomplished by adjusting the command pressure to the command pressure line 270 , which supplies the command pressure volume 260 in contact with the first end 220 of the plunger 220 . The force produced by the pressure (or pressure) on the surface can be determined by the following equation.

[0051] force = pressure * area of ​​surface acting on [1]

[0052] In the case of the exemplary plunger 220 , the force acting on the plunger from the left is equal to the hydraulic pressure (or pressure) achieved within the commanded pressure volume 260 multiplied by the surface area of ​​the first end 222 . The increase in pressure within the commanded pressure volume 260 also increases the force acting on the plunger 220 from the side of the first end 222 . The valve return spring 250 applies a force to the second end 224 of the plunger 220 that acts as a restoring force in a direction opposite the direction of the pressure within the commanded pressure volume 260 . The force from the pressure within the volume 260 and the force from the spring 250 work together such that an increase in pressure within the commanded pressure volume 260 tends to move the plunger 220 in one direction, while a decrease in pressure within the commanded pressure volume 260 tends to move the plunger 220 in one direction. The plunger 220 is moved in the opposite direction. The example regulator valve 210 includes another feature having a feedback line 278 . Hydraulic oil flowing through clutch supply line 276 additionally flows through or is pressurized through feedback line 278 . Hydraulic oil from feedback line 278 re-enters regulator valve 210 and is within feedback pressure volume 265 on the same side of plunger 220 as spring 250 . The force resulting from the hydraulic pressure within the feedback pressure volume 265 acting on the plunger 220 cancels the force resulting from the hydraulic pressure within the command pressure volume 260 . The result is that clutch supply line 276 associated with a clutch fill event where the balance of the force resulting from the pressure within command pressure volume 260 and the force due to spring 250 will place plunger 220 in the position associated with the full supply state The magnitude of the elevated pressure achieved in the interior creates a force that acts on the plunger 220 away from the fully-supplied state position. Calibration and/or control of the feedback line 278 and the resulting force on the plunger 220 corresponding to the selected pressure within the commanded pressure volume 260 can result in a self-correcting plunger position between opposite ends of plunger travel, thereby achieving Partially overlapping state. This partial overlap state is useful for adjusting the pressure achieved within the clutch, such as to achieve calibrated control of the clutch's contact state. Still achievable by setting the pressure within command pressure volume 260 to apply a force to plunger 220 that exceeds the resultant force of the force exerted by spring 250 and the force resulting from hydraulic pressure within feedback pressure volume 265 The full supply state is independent of the operation of the feedback pipeline 278 . Regulator valve 210 includes a pressure switch 240 supplied by pressure switch line 280 and used in known control methods to indicate the pressure level required for control of regulator valve 210 . As such, the regulator valve 210 may selectively direct hydraulic oil to achieve various states within the hydraulically actuated clutch.

[0053] By adjusting the command pressure, the regulator valve of the above exemplary configuration can operate in three states. The high command pressure commands a full supply state, allowing the P LINE Fully exposed to the filled clutch. A low command pressure or null command pressure then commands a venting condition, hindering P LINE Access the clutch and provide a path for hydraulic pressure to drain from the clutch. The intermediate command pressure or the calibration command pressure commands a partial overlap state. The functionality of the partial overlap state depends on the calibration of the calibration command pressure. An exemplary function of such a partial overlap state is to command a contact state in the clutch, thereby enabling a gradual ramp-up of pressure between the clutch discs. Selective calibration of the commanded pressure to achieve the partial overlap condition, in combination with monitoring operation of the pressure switch, allows for precise selection of the fill level within the clutch, eg, the fill level corresponding to a contact condition in the clutch.

[0054] A number of regulator valve physical configurations can be used to perform the described functions. As noted above, one exemplary regulator valve configuration employs a cylindrical plunger within a cylindrical housing. However, the present invention is not intended to be limited to the specific exemplary embodiments described herein.

[0055] The pressure switch 240 is calibrated to indicate that a certain level of pressure has been reached. A pressure switch, for example, can be used to indicate a positive signal only when the regulator valve is in full supply. In this exemplary use, the calibration of the indication of the pressure switch need not correspond to the actual pressure to which the pressure switch is exposed, such as the pressure level in the commanded pressure volume 260; When exposed to pressurized hydraulic fluid, the pressure will always exceed this rated level.

[0056] The regulator valve 210 described above operates based on the command pressure delivered through the command pressure line 270 . An exemplary means of providing the command pressure is a variable flow solenoid valve (or variable flow solenoid), which transmits the low flow command pressure to the regulator valve 210 described above.

[0057] The regulator valve 210 described above is one exemplary device for controlling hydraulic pressure within a system. Other devices are known to operate equivalently to the exemplary regulator valve. For example, variable force solenoid valves (or variable force solenoids) are known to operate similarly to low flow variable flow solenoid valves, except that no regulator valve is required and the variable force solenoid valve directly delivers high flow at the desired pressure to the clutch. Numerous clutch control system embodiments are known. The present invention is not intended to be limited to such figure 1 the described exemplary embodiment.

[0058] The above-mentioned regulating valve 210 adopts the pressure switch 240 to monitor the state of the regulating valve 210 . Such a pressure switch provides a binary signal that indicates whether the monitored pressure exceeds a predetermined threshold pressure that is calibrated or adjusted by the switch. The above-described method of controlling the clutch actuation device can use this binary signal to estimate the operation of the regulator valve 210 and the resulting filling, purging or operation of the clutch. However, it will be appreciated that this control is still an open loop control event.

[0059] figure 2 An exemplary hydraulically actuated clutch operated to provide a clamping force on a mechanical clutch in accordance with the present invention is schematically shown. Clutch assembly 300 includes clutch cylinder 320 and mechanical clutch 340 . The clutch cylinder 320 includes a piston 322 and a clutch volume chamber 324 . Pressurized hydraulic fluid at a certain fill pressure enters the clutch volume cavity 324 through hydraulic line 350 . Hydraulic line 350 is fluidly connected to a mechanism for selectively applying hydraulic flow, such as exemplary regulator valve 210 . Hydraulic oil within clutch volume 324 exerts pressure on piston 322 . Piston 322 converts the fill pressure exerted by the hydraulic fluid into force. The force transmitted by piston 322 is used to associate mechanical clutch 340 with the various states required for synchronizing clutch operation as described above. Positive hydraulic pressure is used to fill the clutch volume 324 and move the piston 322 in one direction. As those skilled in the art will appreciate, draining the hydraulic oil in the clutch volume 324 works to some extent to move the piston 322 in the other direction, but cavitation restricts the low pressure hydraulic fluid from effectively moving the piston 322 Ability. As a result, return spring 326 is used to provide force to move piston 322 in this direction to drain hydraulic fluid from clutch volume 324 .

[0060] Mechanical clutch 340 is selectively actuated via force transmission through piston 322 . Mechanical clutch 340 includes clutch coupling surfaces in the form of clutch discs 345 . Clutch disc 345 is connected to rotating members within the transmission. When the mechanical clutch 340 is not actuated, the clutch disc 345 remains disengaged. Rotation of a portion of the clutch discs 345 does not cause rotation of the remaining portion of the clutch discs 345 . When the mechanical clutch 340 is actuated, the clutch discs 345 are brought into contact with adjacent discs, and sufficient friction between the clutch discs 345 creates a locking relationship in which the discs rotate together .

[0061] As mentioned above, exemplary transitions within a hydraulically controlled clutch are controlled by a regulating valve. While pressure switches are known to be used within regulator valves, such as to indicate the position of the plunger in a fill, discharge, or neutral position, the condition of the piston attached to a clutch filled by a regulator valve is not substantially Known as a control device or module for controlling a regulating valve. Similarly, with the variable force solenoid valve described above, a calibrated solenoid valve setting can be used to deliver pressurized fluid to the clutch. However, while the calibration settings of the solenoid valve and the actuation period of the solenoid valve are known, the resulting state, including any changes from the calibration settings, is not known. By any of the above methods, filling and draining hydraulic fluid into and out of the clutch volume are open loop controls in which calibrated timing and fill pressure are used to achieve desired results in the clutch volume and associated clutch. However, it will be appreciated that such open loop control has inherent inaccuracies, and variations in the system can result in inaccuracies in piston actuation. This inaccuracy can lead to inefficient clutch operation, such as requiring longer calibration fill and drain times to account for changes in the system. Furthermore, such inaccuracies can lead to flares in transmission operation (ie, rapid increases in slip and/or engine speed), tie-ups (ie, undesired gear set engagement) , or other undesired operations.

[0062]Closed-loop control of hydraulically controlled clutches can be used to reduce inaccuracies in the system based on feedback of clutch volume conditions within the clutch, for example allowing better estimation of locked or unlocked conditions in the clutch, and faster Fill and drain times, as well as allowing better control of clutch pressure, eg for clutches in slip mode. However, some known pressure sensors or pressure sensors are too large to be used effectively in a transmission case. Large pressure sensors can make feedback control of hydraulically controlled clutches impractical and impractical. In one exemplary embodiment, a pressure sensor of microelectromechanical systems (MEMS) technology may be used integrally or substantially within a wall defining a hydraulic circuit or hydraulic line, such as within a valve body housing or transmission housing, such that The package space constraints of the transmission are not affected by the addition of a pressure sensor. Such pressure sensors are preferably between 0.020 mm and 1 mm in size and are exposed to hydraulic controls, hydraulic lines, or any suitable portion of the associated clutch volume where the hydraulic pressure is approximately equal to the pressure in the clutch volume 324 . pressure. By monitoring fluid pressure within the circuit connected to the clutch, closed loop feedback control commands can be determined and used to control hydraulic control devices, such as the variable flow solenoid valve or variable force solenoid valve described above, to provide pressurized fluid to the hydraulic circuit. By controlling the pressure within the circuit supplying hydraulic fluid to the clutch based on the monitored pressure within the circuit, the operation of the associated clutch can be more accurately controlled. More accurate control of the clutch minimizes popping and bogging, and allows for quicker gear changes by reducing the need for added time for uncertainty caused by open loop control of the clutch.

[0063] image 3 An exemplary clutch control circuit in accordance with the present invention is schematically shown including a miniaturized pressure sensor for monitoring the pressure within the circuit supplying pressurized fluid to the clutch. The example clutch control loop 400 includes information about figure 1 Several features are described in the circuit 200 , including: the regulator valve 210 , the hydraulic line 270 , and the spool valve plunger 220 . Furthermore, in image 3 Also shown are hydraulic lines 350 that provide pressurized hydraulic fluid to the clutch, such as figure 2 shown. Miniaturized pressure sensor 410 is shown in fluid communication with hydraulic line 350 , monitoring the pressure of the fluid within hydraulic line 350 . Sensor 410 is depicted within the wall of hydraulic line 350 positioned between the hydraulic control device (in this case, regulator valve 210 ) and the device or clutch controlled by the pressurized fluid. However, it will be appreciated that the sensor 410 can be positioned anywhere in the system where the pressure to and from the clutch device can be accurately monitored. For example, the sensor 410 can be located in the wall of the clutch or hydraulic control device instead of the wall of the hydraulic line 350 . Note that if figure 1 Pressure switch 240 as shown can be omitted because a pressure sensor such as sensor 410 can perform the same function that switch 240 can perform in addition to the function performed by sensor 410 (function that switch 240 cannot perform) . The location of sensor 410 is exemplary as the sensor is small enough to exist anywhere within the general structure of the device or system being monitored, so long as the desired pressure can be monitored. Exemplary sensor 410 is depicted as being within the wall of hydraulic line 270 such that packaging constraints for hydraulic line 270 should not be affected by adding sensor 410 . In another embodiment, a sensor 410 can be positioned in the hydraulic line 270 to detect the commanded pressure in order to enable the pressure to and from the clutch device to be accurately estimated or modeled. It will also be appreciated that sensor 410 can comprise any pressure sensor or sensor configuration known in the art.

[0064] It will be appreciated that accurate feedback control of the clutch requires an accurate estimate of the resulting pressure within the clutch volume of the clutch. If the sensor 410 is located some distance from the clutch, it may be necessary to determine the pressure drop, delay or other factors caused by the length of the hydraulic line 350 between the sensor 410 and the clutch. However, experiments have demonstrated that, in some embodiments, the position of the sensor has a detrimental effect on the accuracy of the feedback control based on the sensor output. In accordance with the present invention, pressure sensors or sensors can be used in a number of exemplary locations within a hydraulic circuit. Exemplary locations include, but are not limited to, within the hydraulic control, in the hydraulic line proximate the hydraulic control, in the hydraulic line remote from the hydraulic control and the clutch volume, in the hydraulic line near the clutch piston, and in the inside the clutch volume.

[0065] Figure 4 An exemplary system in accordance with the present invention is depicted that does not operate using the feedback control methods described herein. The horizontal x-axis represents time in seconds. The vertical y-axis describes pressure in kPa. Graph 404 depicts the pressure for an outgoing clutch or a clutch initially in a locked state and commanding the associated hydraulic control device to deliver. Graph 402 depicts the measured pressure of the outgoing clutch. Graph 403 depicts the pressure for an oncoming clutch or a clutch initially in an unlocked state and commanding the associated hydraulic control device to deliver. Graph 401 depicts the measured pressure of the oncoming clutch. Examining graph 404, a large value is initially commanded, resulting in the application of either full line pressure, or maximum clamping pressure, to the clutch that is not reduced. The measured clutch pressures obtained in graph 402 are plotted over the same time. Just before 54 seconds, the activation command was made to purge or drain the clutch in response to an event such as a gear change. As a result, the graph 404 drops below some calibrated value of the measured pressure. With the open loop control described above, the system adjusts and after a certain time delay, the measured pressure decreases. Note, however, that the measured pressure of the outgoing clutch in graph 402 does not track graph 404 well. This inaccuracy can be caused by the open loop and calibration dependent operation of the control as described above. Similarly, examining graph 403, initially commanded a null value, thus yielding a measured pressure of approximately zero in graph 401. At about the same time as graph 404 depicts the initiation of a purge event, graph 403 depicts the initiation of a clutch fill event in which the hydraulic controls are commanded to increase pressure to the clutch. In some embodiments where the empty clutch volume cavity is filled to some extent before any clamping pressure is applied to the clutch, a calibrated fill period is used in which some degree of relatively high pressure or full line pressure is applied, to quickly fill the clutch volume cavity. After this filling period, the pressure can be increased according to the calibrated curve until the clutch can be estimated to be fully locked, after which the commanded pressure can be increased to some high or maximum value, resulting in a maximum clamping force. Graph 403 depicts such an example pressure command operation in which the hydraulic control device is commanded through a series of calibration values ​​to transition the clutch from an unlocked state to a locked state. Graph 401 depicts the measured pressure obtained as a result of the transition transition commanded by graph 403 . Similar to the comparison of graphs 4 and 2 above, graph 401 includes a time lag, thereby tracking graph 403 inaccurately. Additionally, at approximately 54.6 seconds, the commanded pressure is decreasing at this point, while the measured pressure continues to increase and exceed the commanded pressure at that point.

[0066] Figure 4 The data described in describe an example situation in which entanglement between an outgoing clutch and an oncoming clutch is possible. In the outgoing clutch, graph 402 lags and tracks graph 404 poorly, thus causing the outgoing clutch to disengage at a slower rate than commanded, and graph 401 shows that in the outgoing clutch The measured pressure of , increases regardless of the decrease in the commanded pressure in graph 403 . As a result, at approximately 54.6 seconds, both clutches have a significantly higher measured pressure than that commanded by the curves of graphs 404 and 403 . This increased pressure can cause one or both of the clutches to be engaged when they are intended to disengage according to the calibration curve of the commanded pressure. While shifts and related clutch transitions can be commanded by the described system, including inaccuracies and hysteresis of the parameters, such operation requires accurate estimation of hysteresis, inaccuracy and impact hysteresis and inaccuracy both factors.

[0067] Figure 5 An exemplary system in accordance with the present invention is shown that operates using the exemplary feedback control methods described herein. The horizontal x-axis describes time in seconds. The vertical y-axis describes pressure in kPa. Figure 5 Figures 501-504 in the Figure 4 Similar parameters in graphs 401-404. Graph 504 depicts the pressure for an off-going clutch or a clutch initially in a locked state and commanding the associated hydraulic control device to deliver, using feedback from sensor 410 as described herein. Graph 502 depicts the measured pressure for the outgoing clutch. Graph 503 depicts the pressure for an oncoming clutch or a clutch initially in an unlocked state and commanding the associated hydraulic control device to deliver, using feedback from second sensor 410 as described herein. Graph 501 depicts the measured pressure for the oncoming clutch. Examining graphs 504 and 502 and graphs 503 and 501 reveals that measured pressures 502 and 501 are compared to Figure 4 The graphs in , more closely track their corresponding command values.

[0068] Graph 506 depicts the operation of the feedback control method of the hydraulic control device in relation to the outgoing clutch. Graph 506 depicts an exemplary scheme by which the pressure feedback control of the off-going clutch operates to control the command of the off-going clutch, thereby describing a binary on or off operation of the feedback control. In one embodiment, pressure feedback control of the off-going clutch may begin immediately upon initiation of a purge or bleed event and can be maintained throughout the clutch transition. In other embodiments, such as Figure 5 As shown, feedback control can begin as soon as a purge event is initiated and control pressure over some short period of time (including part of the overall clutch transition period) to unload the associated clutch according to the desired curve until the clutch pressure increases significantly until it decreases. After this short period of time, feedback control can end and control can include an open loop or maximum bleed command to quickly bring clutch pressure to zero.

[0069] Graph 505 depicts the operation of the feedback control method of the hydraulic control device in relation to the oncoming clutch. In one embodiment, pressure feedback control of the oncoming clutch can begin immediately upon initiation of a fill event. In another embodiment, a fill period utilizing an open loop or maximize command can be used to rapidly fill the empty clutch volume of the oncoming clutch. like Figure 5 As shown, the pressure feedback control of the oncoming clutch may be delayed and can be activated after a fill event has occurred for a certain determined or calibrated period after the fill period described above. In another embodiment, the monitored pressure sensor can be used to determine when a fill event has reached a sufficient threshold to end the fill event, or to determine that a threshold fill event has occurred to initiate feedback control of an oncoming clutch. Through the use of feedback control of the outgoing clutch and the oncoming clutch (this is accomplished by locating sensors 410 in each clutch device or associated hydraulic device), transitions of clutch states and associated gear states can be coordinated.

[0070] like Figure 5As shown and as shown by the interaction of the various graphs, the control of the outgoing clutch and the oncoming clutch can be coordinated to allow for smooth transition transitions between gear states. This coordination, including feedback responses, can be accomplished according to a number of command curves. The profiles used to control the two clutches may include calibrated responses, where both clutches start their calibrated profiles from a common start time. In another example, measurements from one miniaturized sensor can be used to control pressure in another hydraulic circuit. For example, control of the outgoing clutch can be based on the pressure within the outgoing clutch. Such control can include comparing the pressure in the other clutch to a threshold pressure, or include a functional response based on the measured pressure in the other clutch. Thereby, the transition of the clutch state and the associated gear state can be performed in a manner that avoids unintended operation of the associated transmission.

[0071] The above methods describe miniaturized pressure sensors or sensors arranged to monitor pressure within a hydraulic circuit. image 3 A sensor positioned generally within a cavity of a wall of a hydraulic circuit is described. It will be appreciated, however, that the pressure sensor can be positioned to monitor the pressure within the hydraulic circuit according to a number of alternative configurations. For example, the sensor can be inserted so as to be present in the hydraulic line, or in some physical recess in the circuit, rather than physically located such as image 3 within the walls shown, and still remain consistent with the methods described herein. This configuration can allow the methods described herein to be employed without interfering with packaging constraints of various components within the transmission. Miniaturized pressure sensors can be positioned at a number of different locations within the circuit that delivers pressurized fluid to hydraulically actuated clutches, including: within hydraulic controls, within hydraulic lines proximate to hydraulic controls, remotely from hydraulic controls, and Within the hydraulic line of the clutch volume of the hydraulically actuated clutch, within the hydraulic line proximate the clutch volume of the hydraulically actuated clutch, or within the clutch volume of the hydraulically actuated clutch. Furthermore, as mentioned above, sensors can be provided in the command pressure hydraulic line that controls the hydraulic control device. The physical configuration of the sensors within the described and depicted hydraulic circuits are exemplary embodiments of the disclosed methods, but the invention is not intended to be limited to the specific examples provided herein.

[0072] The above methods describe the use of feedback control, such as PID control, to monitor signals from miniaturized sensors to control a hydraulically actuated clutch device. However, this method need not be used in isolation. For example, feedback control can be combined with feedforward control to achieve improved control of the clutch arrangement. Feedforward control methods monitor a number of parameters or inputs that describe the operation of the system, and determine as output the predicted desired control of the system being controlled. The output of the feedforward model can be determined experimentally, empirically, by prediction, by modeling, and by other techniques sufficient to accurately predict transmission operation, and a large number of calibration curves can be used for the same transmission , for use with different powertrain settings, conditions or operating ranges.

[0073] The above-described method can operate within a control module. The control module can be embodied within a single device to perform the methods described herein. In other embodiments, the control module is located within or as part of a larger control module, such as within a transmission control module. In other embodiments, a control module can describe functions that execute within a plurality of physical devices and operate to perform the method.

[0074] Control module, module, controller, control unit, processor, and similar terms mean any suitable one of the following, or various combinations of one or more of the following, said each being : Application Specific Integrated Circuits (ASICs), electronic circuits, a central processing unit (preferably a microprocessor) executing one or more software or firmware programs and associated memory and storage (read-only, programmable read-only, random access) access, hard disk drives, etc.), combinational logic circuits, input/output circuits and devices, suitable signal conditioning and buffering circuits, and other suitable components that provide the above functions. The control module has a set of control algorithms, including resident software program instructions and calibrations that are stored in memory and executed to provide the desired functionality. The algorithm is preferably executed during preset cycles. Algorithms are executed, for example, by a central processing unit, and are operable to monitor inputs from sensing devices and other networked control modules, and execute control and diagnostic routines to control operation of actuators. Cycles can be executed at regular intervals, such as every 3.125, 6.25, 12.5, 25, and 100 milliseconds, during ongoing engine and vehicle operation. Alternatively, an algorithm can be executed in response to the occurrence of an event.

[0075] The present invention has described some preferred embodiments and variations thereof. After reading and understanding the specification, other variations and modifications will occur to those skilled in the art. Therefore, the present invention is not intended to be limited to the specific embodiments disclosed as the best modes contemplated for carrying out the invention, but the present invention is to include all embodiments falling within the scope of the appended claims.