Patent Description:
In a conventional powered machine, a prime mover can operate at different speeds and produce different levels of power that is transferred to a transmission. In one instance, the prime mover can be an engine. In turn, the transmission can transfer torque to a driveline or final drive assembly, which can be directly mounted to the wheels or tracks of the powered machine. The transmission can include an internal pump that is rotatably driven by the prime mover, and based on the different speeds of the prime mover, the pump can produce different levels of fluid flow and pressure. In some instances, there is only one internal pump in the transmission that provides fluid flow to a main pressure circuit and lube circuit of the transmission.

A conventional hydraulic pump is often designed as a result of its desired functionality. In an engine-transmission application, for example, a conventional hydraulic pump may be designed for one of several reasons, namely, <NUM>) to provide adequate fluid flow at a low engine idle speed (e.g., approximately <NUM> RPM), <NUM>) to provide full regulated pressure to the main pressure circuit of the transmission at a specific engine speed (e.g., approximately <NUM> RPM), and/or <NUM>) to fill a transmission clutch within a desired time period (e.g., approximately <NUM> at <NUM> RPM). Other design considerations may include margin of safety and leakage at a fluid temperature of about <NUM>. In view of the different design considerations accounted for in a hydraulic pump, however, the pump still often tends to overproduce fluid flow at or above normal operating conditions and engine speeds.

Moreover, once the hydraulic pump is able to provide adequate fluid flow to the control and lube systems of the transmission, additional fluid flow produced by the pump is generally returned to transmission sump and is unusable. This excess fluid flow, however, directly contributes to hydraulic spin-loss inside the transmission. In effect, this reduces transmission productivity and performance.

One possible solution to the excess flow produced by the hydraulic pump is to incorporate a variable displacement pump into the transmission design. A variable displacement pump can increase or decrease volume inside the fluid cavity of the pump, thereby controlling the pump displacement and production of fluid flow. By controlling displacement, the pump can produce a more desirable amount of flow under steady-state conditions. When the transmission is in a certain range, for example, the hydraulic demand is usually fairly low and the volume of the oil cavity can be decreased, thereby resulting is reduced overall pump flow. Likewise, during a shift between ranges, the hydraulic demand increases for filling a clutch such that the volume of the oil cavity is increased and more flow is produced to meet demand.

Since the "decrease" pressure is based off of pressure in the main circuit, however, there is an inherit response time drawback. In other words, the demand to increase fluid flow (e.g., when filling a clutch) begins before the volume of the pump cavity increases ("decrease" pressure responds). Thus, regardless of what improvements are made to the pump and transmission system, the hydraulic demand rises before the pump can supply the desired flow, thereby resulting in an undesirable time delay to fill the clutch. This can impact fuel economy and shift quality. An example a system for selectively routing transmission fluid to a torque converter is described in <CIT>. The system comprises a first pump configured to supply transmission fluid from a source of transmission fluid to a plurality of electro-hydraulic components within a transmission. A second pump is configured to supply transmission fluid from the source of transmission fluid to a lubrication system of the transmission. A valve is configured to route transmission fluid supplied by the second pump through the torque converter to the lubrication system during the torque converter operating mode. The system also comprises means for selectively routing at least some of the transmission fluid supplied by the first pump through the torque converter. Additionally, an example of a regulation of hydraulic pressure in a system having multiple pressure sources is described in <CIT>.

A need therefore exists for electronically controlling the pump capacity of the transmission. By controlling pump capacity, it is also desirable to control fluid flow from the pump to minimize excess flow once the different fluid circuits of the transmission are satisfied, improve shift quality, and control fluid temperature of the transmission.

Herein is also disclosed an example of a hydraulic system of a transmission includes a controller and a variable displacement pump. The pump is adapted to be driven by a torque-generating mechanism and includes an inlet and an outlet. Moreover, the pump is configured to generate fluid flow and pressure throughout the system. The system also includes a main circuit fluidly coupled to the pump and a main regulator valve disposed in the main circuit. The main regulator valve is configured to move between at least a regulated position and an unregulated position, where the regulated position corresponds to a regulated pressure in the main circuit. A pressure switch is fluidly coupled to the main regulator valve and configured to move between a first position and a second position, where the switch is disposed in electrical communication with the controller. A solenoid is disposed in electrical communication with the controller, such that the solenoid is controllably coupled to the pump to alter the displacement of the pump.

In one aspect of this example, once the fluid pressure in the main circuit reaches a substantially regulated condition, the main regulator valve moves from the unregulated position to the regulated position. In another aspect, the pressure switch is configured to detect the movement of the main regulator valve between the regulated position and unregulated position and the pressure switch moves between the first position and the second position upon movement of the main regulator valve. In a further aspect, the movement of the pressure switch between the first position and second position induces a signal triggered to the controller such that the controller controllably actuates the solenoid based on the signal. In yet a further aspect, the pump displacement is controllable between a first displacement and a second displacement, where the fluid flow distributed from the outlet is adjustably controlled based on the pump displacement and the actuation of the solenoid controllably adjusts pump displacement.

In a different aspect of this example, a lube circuit is fluidly coupled to the pump and main circuit and a lube regulator valve is disposed in the lube circuit. The lube regulator valve is configured to move between at least a regulated position and an unregulated position, where the regulated position corresponds to a regulated pressure in the lube circuit. A second pressure switch is fluidly coupled to the lube regulator valve and configured to move between a first position and a second position, where the second pressure switch is disposed in electrical communication with the controller.

Related thereto, the lube regulator valve moves to its regulated position after the main regulator valve moves to its regulated position. Moreover, the lube regulator valve moves from the unregulated position to the regulated position once the fluid pressure in the lube circuit reaches a substantially regulated condition and the second pressure switch is configured to detect the movement of the lube regulator valve between the regulated position and unregulated position, where the pressure switch moves between the first position and the second position upon movement of the main regulator valve. Further related thereto, the movement of the second pressure switch between the first position and second position induces a signal triggered to the controller and the controller controllably actuates the solenoid based on the signal to adjust displacement of the pump.

The hydraulic system of a transmission includes a controller and a variable displacement pump. The pump is adapted to be driven by a torque-generating mechanism and includes an inlet and an outlet. Moreover, the pump is configured to generate fluid flow and pressure throughout the system. The system also includes a lube circuit fluidly coupled to the pump and a lube regulator valve disposed in the lube circuit. The lube regulator valve is configured to move between at least a regulated position and an unregulated position, where the regulated position corresponds to a regulated pressure in the lube circuit. A pressure switch is fluidly coupled to the lube regulator valve and configured to move between a first position and a second position, where the switch is disposed in electrical communication with the controller. A solenoid is disposed in electrical communication with the controller, such that the solenoid is controllably coupled to the pump to alter the displacement of the pump.

In one aspect of this example, once the fluid pressure in the lube circuit reaches a substantially regulated condition, the lube regulator valve moves from the unregulated position to the regulated position. In another aspect, the pressure switch is configured to detect the movement of the lube regulator valve between the regulated position and unregulated position and the pressure switch moves between the first position and the second position upon movement of the lube regulator valve. Related thereto, the movement of the pressure switch between the first position and second position induces a signal triggered to the controller and the controller controllably actuates the solenoid based on the signal. In a further aspect, the pump displacement is controllable between a first displacement and a second displacement, where the fluid flow distributed from the outlet is adjustably controlled based on the pump displacement and the actuation of the solenoid controllably adjusts pump displacement.

In an alternative aspect, the system can include a main circuit fluidly coupled to the pump and lube circuit and a main regulator valve disposed in the main circuit. The main regulator valve is configured to move between at least a regulated position and an unregulated position, where the regulated position corresponds to a regulated pressure in the main circuit. In addition, a second pressure switch is fluidly coupled to the main regulator valve and configured to move between a first position and a second position, where the second pressure switch is disposed in electrical communication with the controller. In a similar aspect, the solenoid is controllably actuates between a first condition and a second condition upon movement of at least one of the main regulator valve and the lube regulator valve to its regulated position.

The system includes a temperature sensor disposed in electrical communication with the controller. The temperature sensor is adapted to detect a temperature of the fluid in the transmission. The system can also include a cooler circuit fluidly coupled to the pump and main circuit, where the cooler circuit is structured to receive fluid and adjust its temperature as the fluid passes therethrough. Here, the temperature sensor is structured to detect the fluid temperature in the transmission and communicate said temperature to the controller. In turn, the controller controllably actuates the solenoid from a first electrical state to a second electrical, where the actuation between the first electrical state and the second electrical state adjusts the rate of fluid flow passing through the cooler circuit.

In a further example, a method is provided for controlling fluid flow through a transmission. The transmission includes a controller, a variable displacement pump having an inlet and an outlet, a main circuit fluidly coupled to the pump, a lube circuit fluidly coupled to the pump and main circuit, a main regulator valve, a lube regulator valve, a pressure switch, and a solenoid. Here, the method includes pumping fluid from the pump into the main circuit until the fluid pressure in the main circuit reaches a first regulation point and fluidly actuating the main regulator valve from an unregulated position to a regulated position when the fluid pressure in the main circuit reaches the first regulation point. The method also includes pumping fluid into the lube circuit until the fluid pressure in the lube circuit reaches a second regulation point and fluidly actuating the lube regulator valve from an unregulated position to a regulated position when the fluid pressure in the lube circuit reaches the second regulation point. Moreover, the method includes moving the pressure switch from a first position to a second position and detecting the movement of the pressure switch from the first position to the second position. The solenoid is actuated from a first electrical state to a second electrical state and the displacement of the pump is adjusted from a first displacement to a second displacement.

In one aspect of this example, the method can include controlling a rate of fluid flow pumped from the outlet. The method can also include increasing the displacement of the pump to increase the rate of fluid flow pumped from the outlet. Alternatively, the method can include decreasing the displacement of the pump to decrease the rate of fluid flow pumped from the outlet. In another aspect, the method includes detecting a fluid temperature with a temperature sensor, sending a signal to the controller based on the detected temperature, and adjusting the rate of fluid flow from the pump outlet until the detected temperature reaches a desired temperature. In a further aspect, the method can include triggering the pressure switch from the first position to the second position when the fluid pressure in the main circuit reaches the first regulation point or when the fluid pressure in the lube circuit reaches the second regulation point.

In an alternative aspect, the method includes moving a second pressure switch from a first position to a second position and detecting the movement of the second pressure switch from the first position to the second position. Related thereto, the method can include triggering the second pressure switch from the first position to the second position when either the fluid pressure in the main circuit reaches the first regulation point or the fluid pressure in the lube circuit reaches the second regulation point. Moreover, the solenoid is actuated from the first electrical state to the second electrical state when either the first pressure switch is moved from its first position to its second position or the second pressure switch is moved from its first position to its second position.

The above-mentioned aspects of the present invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention, taken in conjunction with the accompanying drawings, wherein:.

The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention.

Referring now to <FIG>, a block diagram and schematic view of one illustrative embodiment of a vehicular system <NUM> having a drive unit <NUM> and transmission <NUM> is shown. In the illustrated embodiment, the drive unit <NUM> may include an internal combustion engine, diesel engine, electric motor, or other power-generating device. The drive unit <NUM> is configured to rotatably drive an output shaft <NUM> that is coupled to an input or pump shaft <NUM> of a conventional torque converter <NUM>. The input or pump shaft <NUM> is coupled to an impeller or pump <NUM> that is rotatably driven by the output shaft <NUM> of the drive unit <NUM>. The torque converter <NUM> further includes a turbine <NUM> that is coupled to a turbine shaft <NUM>, and the turbine shaft <NUM> is coupled to, or integral with, a rotatable input shaft <NUM> of the transmission <NUM>. The transmission <NUM> can also include an internal pump <NUM> for building pressure within different flow circuits (e.g., main circuit, lube circuit, etc.) of the transmission <NUM>. The pump <NUM> can be driven by a shaft <NUM> that is coupled to the output shaft <NUM> of the drive unit <NUM>. In this arrangement, the drive unit <NUM> can deliver torque to the shaft <NUM> for driving the pump <NUM> and building pressure within the different circuits of the transmission <NUM>.

The transmission <NUM> can include a planetary gear system <NUM> having a number of automatically selected gears. An output shaft <NUM> of the transmission <NUM> is coupled to or integral with, and rotatably drives, a propeller shaft <NUM> that is coupled to a conventional universal joint <NUM>. The universal joint <NUM> is coupled to, and rotatably drives, an axle <NUM> having wheels 134A and 134B mounted thereto at each end. The output shaft <NUM> of the transmission <NUM> drives the wheels 134A and 134B in a conventional manner via the propeller shaft <NUM>, universal joint <NUM> and axle <NUM>.

A conventional lockup clutch <NUM> is connected between the pump <NUM> and the turbine <NUM> of the torque converter <NUM>. The operation of the torque converter <NUM> is conventional in that the torque converter <NUM> is operable in a so-called "torque converter" mode during certain operating conditions such as vehicle launch, low speed and certain gear shifting conditions. In the torque converter mode, the lockup clutch <NUM> is disengaged and the pump <NUM> rotates at the rotational speed of the drive unit output shaft <NUM> while the turbine <NUM> is rotatably actuated by the pump <NUM> through a fluid (not shown) interposed between the pump <NUM> and the turbine <NUM>. In this operational mode, torque multiplication occurs through the fluid coupling such that the turbine shaft <NUM> is exposed to drive more torque than is being supplied by the drive unit <NUM>, as is known in the art. The torque converter <NUM> is alternatively operable in a so-called "lockup" mode during other operating conditions, such as when certain gears of the planetary gear system <NUM> of the transmission <NUM> are engaged. In the lockup mode, the lockup clutch <NUM> is engaged and the pump <NUM> is thereby secured directly to the turbine <NUM> so that the drive unit output shaft <NUM> is directly coupled to the input shaft <NUM> of the transmission <NUM>, as is also known in the art.

The transmission <NUM> further includes an electro-hydraulic system <NUM> that is fluidly coupled to the planetary gear system <NUM> via a number, J, of fluid paths, <NUM><NUM>-<NUM>J, where J may be any positive integer. The electro-hydraulic system <NUM> is responsive to control signals to selectively cause fluid to flow through one or more of the fluid paths, <NUM><NUM>-<NUM>J, to thereby control operation, i.e., engagement and disengagement, of a plurality of corresponding friction devices in the planetary gear system <NUM>. The plurality of friction devices may include, but are not limited to, one or more conventional brake devices, one or more torque transmitting devices, and the like. Generally, the operation, i.e., engagement and disengagement, of the plurality of friction devices is controlled by selectively controlling the friction applied by each of the plurality of friction devices, such as by controlling fluid pressure to each of the friction devices. In one example embodiment, which is not intended to be limiting in any way, the plurality of friction devices include a plurality of brake and torque transmitting devices in the form of conventional clutches that may each be controllably engaged and disengaged via fluid pressure supplied by the electro-hydraulic system <NUM>. In any case, changing or shifting between the various gears of the transmission <NUM> is accomplished in a conventional manner by selectively controlling the plurality of friction devices via control of fluid pressure within the number of fluid paths <NUM><NUM>-<NUM>J.

The system <NUM> further includes a transmission control circuit <NUM> that can include a memory unit <NUM>. The transmission control circuit <NUM> is illustratively microprocessor-based, and the memory unit <NUM> generally includes instructions stored therein that are executable by the transmission control circuit <NUM> to control operation of the torque converter <NUM> and operation of the transmission <NUM>, i.e., shifting between the various gears of the planetary gear system <NUM>. It will be understood, however, that this disclosure contemplates other embodiments in which the transmission control circuit <NUM> is not microprocessor-based, but is configured to control operation of the torque converter <NUM> and/or transmission <NUM> based on one or more sets of hardwired instructions and/or software instructions stored in the memory unit <NUM>.

In the system <NUM> illustrated in <FIG>, the torque converter <NUM> and the transmission <NUM> include a number of sensors configured to produce sensor signals that are indicative of one or more operating states of the torque converter <NUM> and transmission <NUM>, respectively. For example, the torque converter <NUM> illustratively includes a conventional speed sensor <NUM> that is positioned and configured to produce a speed signal corresponding to the rotational speed of the pump shaft <NUM>, which is the same rotational speed of the output shaft <NUM> of the drive unit <NUM>. The speed sensor <NUM> is electrically connected to a pump speed input, PS, of the transmission control circuit <NUM> via a signal path <NUM>, and the transmission control circuit <NUM> is operable to process the speed signal produced by the speed sensor <NUM> in a conventional manner to determine the rotational speed of the turbine shaft <NUM>/drive unit output shaft <NUM>.

The transmission <NUM> illustratively includes another conventional speed sensor <NUM> that is positioned and configured to produce a speed signal corresponding to the rotational speed of the transmission input shaft <NUM>, which is the same rotational speed as the turbine shaft <NUM>. The input shaft <NUM> of the transmission <NUM> is directly coupled to, or integral with, the turbine shaft <NUM>, and the speed sensor <NUM> may alternatively be positioned and configured to produce a speed signal corresponding to the rotational speed of the turbine shaft <NUM>. In any case, the speed sensor <NUM> is electrically connected to a transmission input shaft speed input, TIS, of the transmission control circuit <NUM> via a signal path <NUM>, and the transmission control circuit <NUM> is operable to process the speed signal produced by the speed sensor <NUM> in a conventional manner to determine the rotational speed of the turbine shaft <NUM>/transmission input shaft <NUM>.

The transmission <NUM> further includes yet another speed sensor <NUM> that is positioned and configured to produce a speed signal corresponding to the rotational speed of the output shaft <NUM> of the transmission <NUM>. The speed sensor <NUM> may be conventional, and is electrically connected to a transmission output shaft speed input, TOS, of the transmission control circuit <NUM> via a signal path <NUM>. The transmission control circuit <NUM> is configured to process the speed signal produced by the speed sensor <NUM> in a conventional manner to determine the rotational speed of the transmission output shaft <NUM>.

In the illustrated embodiment, the transmission <NUM> further includes one or more actuators configured to control various operations within the transmission <NUM>. For example, the electro-hydraulic system <NUM> described herein illustratively includes a number of actuators, e.g., conventional solenoids or other conventional actuators, that are electrically connected to a number, J, of control outputs, CP<NUM> - CPJ, of the transmission control circuit <NUM> via a corresponding number of signal paths <NUM><NUM> - <NUM>J, where J may be any positive integer as described above. The actuators within the electro-hydraulic system <NUM> are each responsive to a corresponding one of the control signals, CP<NUM> - CPJ, produced by the transmission control circuit <NUM> on one of the corresponding signal paths <NUM><NUM> - <NUM>J to control the friction applied by each of the plurality of friction devices by controlling the pressure of fluid within one or more corresponding fluid passageway <NUM><NUM> - <NUM>J, and thus control the operation, i.e., engaging and disengaging, of one or more corresponding friction devices, based on information provided by the various speed sensors <NUM>, <NUM>, and/or <NUM>. The friction devices of the planetary gear system <NUM> are illustratively controlled by hydraulic fluid which is distributed by the electro-hydraulic system in a conventional manner. For example, the electro-hydraulic system <NUM> illustratively includes a conventional hydraulic positive displacement pump (not shown) which distributes fluid to the one or more friction devices via control of the one or more actuators within the electro-hydraulic system <NUM>. In this embodiment, the control signals, CP<NUM> - CPJ, are illustratively analog friction device pressure commands to which the one or more actuators are responsive to control the hydraulic pressure to the one or more frictions devices. It will be understood, however, that the friction applied by each of the plurality of friction devices may alternatively be controlled in accordance with other conventional friction device control structures and techniques, and such other conventional friction device control structures and techniques are contemplated by this disclosure. In any case, however, the analog operation of each of the friction devices is controlled by the control circuit <NUM> in accordance with instructions stored in the memory unit <NUM>.

In the illustrated embodiment, the system <NUM> further includes a drive unit control circuit <NUM> having an input/output port (I/O) that is electrically coupled to the drive unit <NUM> via a number, K, of signal paths <NUM>, wherein K may be any positive integer. The drive unit control circuit <NUM> may be conventional, and is operable to control and manage the overall operation of the drive unit <NUM>. The drive unit control circuit <NUM> further includes a communication port, COM, which is electrically connected to a similar communication port, COM, of the transmission control circuit <NUM> via a number, L, of signal paths <NUM>, wherein L may be any positive integer. The one or more signal paths <NUM> are typically referred to collectively as a data link. Generally, the drive unit control circuit <NUM> and the transmission control circuit <NUM> are operable to share information via the one or more signal paths <NUM> in a conventional manner. In one embodiment, for example, the drive unit control circuit <NUM> and transmission control circuit <NUM> are operable to share information via the one or more signal paths <NUM> in the form of one or more messages in accordance with a society of automotive engineers (SAE) J-<NUM> communications protocol, although this disclosure contemplates other embodiments in which the drive unit control circuit <NUM> and the transmission control circuit <NUM> are operable to share information via the one or more signal paths <NUM> in accordance with one or more other conventional communication protocols.

In the present disclosure, a system and method is disclosed for improving fluid flow through a hydraulic system of a transmission. The system and method can be for a hydraulic control system that utilizes hydraulic and electrical control features to improve stability, efficiency, and performance of the hydraulic system. Through these improvements, other factors such as transmission performance and fuel economy can be improved. Moreover, the present disclosure describes a model-based approach for achieving improvements in the control and performance of the hydraulic system and the transmission. Some aspects of the present disclosure can be incorporated into downloadable and readable software or instructions stored in the memory unit <NUM> of the control circuit <NUM>.

In this disclosure, the transmission control circuit <NUM> may be interchangeably referred to as a transmission controller, or controller. In the event an engine control circuit is described, the engine control circuit may be referred to as an engine controller. In addition, fluid flow through the hydraulic system of the transmission can be described with respect to pressure and flow rate. Other characteristics of the fluid flow, such as temperature, may also be described. When the terms "fluid flow" is disclosed herein, it is intended to refer to the flow rate or volume of fluid flow passing through a point in the hydraulic system, whereas "fluid pressure" refers to the actual pressure of the fluid at a designated location in the system.

In a conventional hydraulic system of a transmission, a pump is rotationally driven by a torque-generating mechanism such as a torque converter. In some aspects, a prime mover or engine output may rotationally drive the pump. The pump can be a gerotor pump, a crescent-style pump, a variable displacement pump, or any other known pump. As the pump is rotationally driven, fluid can be collected through an inlet or suction port of the pump. As the pump rotates, fluid pressure and flow builds and the fluid is pumped through an outlet of the pump and into a main hydraulic circuit, or main circuit, of the hydraulic system. The fluid passing through the main circuit has a defined pressure, referred to as main pressure. The fluid can be pumped through the main circuit, and this pressure can be controlled by a valve. In this disclosure, the valve is referred to as a main regulator valve.

As the fluid is pumped into the main circuit, the main pressure can reach a steady-state condition. In one aspect, a solenoid can modulate or control the main pressure in the system. When there is a demand for fluid, e.g., to fill an oncoming clutch, the main pressure in the main circuit may decrease suddenly due to the immediate demand for fluid. The main regulator valve can react more quickly to this immediate demand than the pump. In any event, the lack of fluid pressure in the main circuit is detected and the pump is controlled to pump additional flow into the main circuit. In many conventional arrangements, however, this sudden increase in fluid flow causes an undershoot or depressed main pressure in the system. The delay between the demand and supply of fluid and then the sudden depleted supply of fluid due to the delayed response by the pump can negatively shift quality.

To address this issue, an exemplary hydraulic system <NUM> is illustrated in <FIG>. The hydraulic system <NUM> includes a variable displacement pump <NUM>. The variable displacement pump <NUM> is a pressure-based pump, such that if pressure is regulated in the system <NUM>, the pump <NUM> can output the necessary fluid flow as needed. In other words, if pressure in the system <NUM> decreases, the pump <NUM> increases its flow until the pressure is regulated, and vice versa. To facilitate the regulation of pressure in the system <NUM>, and particularly in the main circuit, a main regulator valve <NUM> is disposed in fluid communication with the pump <NUM>. The main regulator valve <NUM> recognizes the pressure needed in the system <NUM>, and particularly in the main circuit of the system <NUM>. In this manner, the main regulator valve <NUM> acts as a feedback control such that the valve <NUM> strokes or moves between positions until pressure demands are met. In doing so, the main regulator valve <NUM> is controllably stroked against spring pressure exerted by a spring (not shown). The main regulator valve <NUM> can move to one defined position such that excess fluid is directed back to the suction port of the variable displacement pump <NUM>. As a result, the main regulator valve <NUM> acts as a feedback control that converts fluid flow from the pump <NUM> into main pressure.

In <FIG>, fluid is pumped from the outlet of the pump <NUM> along a main flow path <NUM> to the main regulator valve <NUM>, and fluid is directed along hydraulic path <NUM> to satisfy the needs of a main circuit <NUM>. The main circuit <NUM> includes the controls (e.g., clutches) for operating and controlling the transmission. Along the hydraulic path <NUM> is a solenoid <NUM> for modulating or regulating pressure in the main circuit <NUM>. Therefore, the fluid pressure in the main circuit <NUM> can be regulated by the solenoid <NUM>. Until now, however, the fluid flow in the system <NUM> has not been regulated or controlled.

As described, the control of the variable displacement pump <NUM> is via the main regulator valve <NUM>. As the valve <NUM> strokes due to a pressure demand in the system, the pump pressure "decrease" or control changes due to the sudden demand for fluid in the system <NUM>. The delayed response of the pump <NUM> can lead to an undershoot and overshoot of main pressure in the main circuit, which as previously described, can negatively impact the hydraulic system and transmission. To overcome this problem, it can be desirable to better control when the overshoot and undershoot conditions occur, and more specifically, alter or compensate for this by inducing the pressure response under steady-state conditions.

The variable displacement pump <NUM> produces fluid flow based off of input speed of the torque-generating mechanism and pressure. Thus, main pressure increases or decreases as the system pressure increases or decreases, and this is ideal under steady-state conditions. One feature of the present disclosure is compensating for the delayed time response of the pump <NUM> by increasing fluid flow as soon as possible, and preferably before there is a demand in the system due to a clutch fill, for example. Here, the supply of fluid can be initiated before the clutch fill process is initiated, thereby avoiding inconsistent clutch fill times. As such, garage shifts can be improved due to increased flow.

To understand how the fluid flow is controllable in the hydraulic system <NUM> of <FIG>, a second flow path <NUM> and a third flow path <NUM> are fluidly coupled to the main regulator valve <NUM>. As main pressure is regulated in the main circuit <NUM>, the main regulator valve <NUM> can stroke to a new position to enable fluid to pass through the second flow path <NUM> and into a converter circuit <NUM>. The converter circuit <NUM> can be part of the torque converter <NUM> as described above with reference to <FIG>. Fluid can also pass through another flow path <NUM> and into a cooler circuit <NUM>. The cooler circuit <NUM> can have an inlet and an outlet, and a means for regulating or controlling the temperature of fluid passing therethrough.

As the converter circuit <NUM> and cooler circuit <NUM> are satisfied with fluid flow, fluid continues to be pumped via another flow path <NUM> and into a lube circuit <NUM> of the hydraulic system <NUM>. The lube circuit <NUM> enables fluid to lubricate bearings, clutches, shafts, gears, etc. in the transmission. Fluid pressure in the lube circuit <NUM> can be referred to as lube pressure. Similar to main pressure, the hydraulic system <NUM> can include a valve for regulating lube pressure. In this disclosure, the valve is referred to as a lube regulator valve <NUM>. The lube regulator valve <NUM> is fluidly coupled to the lube circuit and is disposed in a location of the system <NUM> after the cooler circuit <NUM>.

The lube regulator valve <NUM> can detect when the lube pressure has regulated in the lube circuit <NUM>. Once lube pressure reaches its regulation point, the lube regulator valve <NUM> strokes or moves to a different position so that additional fluid is directed to a sump <NUM> of the transmission. In the embodiment of <FIG>, the main regulator valve <NUM> can also be in fluid communication with sump <NUM> where excess fluid is directed along the third flow path <NUM> thereto. Similarly, the lube regulator valve <NUM> can direct fluid along a different flow path <NUM> so that excess fluid is dumped to sump <NUM>.

Once the lube regulator valve <NUM> strokes to its regulated position, i.e., the position at which lube pressure has reached its regulation point, a pressure switch <NUM> can detect the movement of the valve <NUM> to this position. This movement can trigger the switch <NUM> to toggle or move to a different electrical state, thereby sending a signal to a controller <NUM> of the transmission. As shown in <FIG>, the controller <NUM> and pressure switch <NUM> can be electrically coupled to one another along a communication path <NUM>. In this manner, the pressure switch <NUM> acts like an input to a closed loop system in which the switch communicates with the controller <NUM>. In turn, the controller <NUM> receives the signal from the switch <NUM> and understands the communication as being an indicator that the lube circuit <NUM> is satisfied. As a result, extra or excess flow is not useful to the hydraulic system <NUM>.

Once the controller <NUM> receives the signal from the pressure switch <NUM>, it can actuate a different solenoid <NUM> for controlling the pump flow. This solenoid can be referred to as a pump control solenoid <NUM> and is disposed along flow path <NUM>. Flow path <NUM> can be fluidly coupled with the decrease port of the variable displacement pump <NUM>. The pump flow can be controlled by altering or changing the displacement of the variable displacement pump <NUM>. Here, the controller <NUM> can communicate with the pump control solenoid <NUM> via communication link <NUM>. Thus, depending on the demands of the hydraulic system <NUM>, the controller <NUM> can communicate with the pump control solenoid <NUM> to either increase or decrease pressure at the decrease port of the pump <NUM>. This thereby increases or decreases the displacement of the pump <NUM>.

A similar approach can be done by regulating main pressure and communicating to the controller <NUM> when main pressure reaches its regulation point. An example of this is shown in <FIG>. Here, an embodiment of a hydraulic system <NUM> includes the pressure switch <NUM> in communication with the lube regulator valve <NUM>. In addition, a second pressure switch <NUM> is disposed in communication with the main regulator valve <NUM>. Therefore, as main pressure regulates and the main regulator valve <NUM> moves to its regulated position, the second pressure switch <NUM> can send a signal to the controller <NUM> via communication link <NUM>. With both pressure switches, the controller <NUM> can more accurately control the needs of the hydraulic system <NUM> by controllably actuating the pump control solenoid <NUM> and thereby controlling pump flow.

In an alternative embodiment, a hydraulic system may only include the pressure switch <NUM> disposed in communication with the main regulator valve <NUM>. In a different embodiment, a second pump may be disposed either along flow path <NUM> or flow path <NUM> to further facilitate fluid flow through the system. This second pump (not shown) may be referred to as a lube pump that can provide higher flow but lower pressure.

One of the advantages of the hydraulic control system in <FIG> and <FIG> is the ability to control fluid temperature in the system. As fluid passes through the cooler circuit <NUM> it enters the lube circuit <NUM> and builds lube pressure. It is desirable to build lube pressure and satisfy the lube circuit <NUM> as quickly as possible. Once lube pressure regulates, it can also be desirable to maintain or control fluid temperature passing through the different circuits. To do so, a temperature sensor <NUM> is disposed in fluid communication with the sump <NUM>. The temperature sensor <NUM> can also be electrically coupled to the controller <NUM> via communication path <NUM>. In some instances, a transmission may operate efficiently such that the fluid temperature operating therein is cooler than desired. This may increase spin losses in the transmission. In other instances, the transmission may be operating where the fluid temperature is hot, which can negatively impact different hardware operating in the transmission. Therefore, an ideal temperature or temperature range may be programmed into the controller <NUM> for maintaining or controlling the fluid temperature at or within the desired range.

During operation, the temperature sensor <NUM> can communicate a current, real-time fluid temperature to the controller <NUM> via communication link <NUM>. In turn, the controller <NUM> can controllably actuate the pump control solenoid <NUM> to adjust pump displacement. By adjusting pump displacement, fluid flow can be controlled from the pump and through the cooler circuit <NUM>. In other words, the pump control solenoid <NUM> can effectively control cooler flow through the cooler circuit <NUM> until the temperature sensor <NUM> detects a fluid temperature that either meets the desired temperature or falls within the desired temperature range. Thus, if the fluid temperature is greater than a desired temperature, the hydraulic control system can increase the fluid flow through the cooler until the fluid temperature decreases to within a desired range. Moreover, if the fluid temperature is cooler than the desired temperature, the hydraulic control system can reduce fluid flow through the cooler circuit <NUM> until the fluid temperature increases. The adjusted fluid flow through the cooler circuit <NUM> can be controlled by the pump control solenoid <NUM> to controllably adjust the fluid temperature operating within the transmission.

Besides controlling temperature, the pump control solenoid <NUM> can also adjust pump flow based on demand. If pressure throughout the lube circuit <NUM> is regulated, the pump control solenoid <NUM> can reduce pump flow so that "extra" or "excess" flow is reduced, thereby reducing spin losses. Thus, it can be desirable for the controller <NUM> to know when lube pressure and main pressure are regulated so that transmission spin losses and efficiency can be improved.

Another aspect to this is being able to adapt to leakage in the hydraulic system. Leakage can vary from transmission to transmission, and this is particularly the case for pump leakage and leakage in the controls. A pump may vary due to side clearances, for example. In any event, the regulation point of both main pressure and lube pressure may differ between hydraulic systems due to the difference in leakage of both systems.

Referring to <FIG>, for example, a graphical representation <NUM> of main pressure as a function of input or engine speed is shown. Here, as engine speed increases, main pressure also increases. A nominal curve <NUM> is shown as being indicative of a nominal or average hydraulic system. A first curve <NUM> and a second curve <NUM> are also shown where the nominal curve <NUM> is disposed therebetween. The first curve <NUM> may represent a hydraulic system with a minimum amount of leakage, and the second curve <NUM> may represent a hydraulic system with a maximum amount of leakage.

In <FIG>, there is a defined regulation pressure <NUM> that is reached at or about a specific engine speed. As engine speed increases, main pressure also increases until it reaches the regulation point. Once main pressure reaches its regulation point, the main regulator valve <NUM> moves to its regulation position and the pressure switch <NUM> can detect this position. The nominal curve <NUM> reaches regulation at a nominal regulation point <NUM>. Similarly, the first curve <NUM> reaches regulation at a first regulation point <NUM> and the second curve <NUM> reaches regulation at a second regulation point <NUM>. As shown, each curve reaches its corresponding regulation point at a different engine speed, thereby illustrating a variance <NUM> in leakage adaptive. As will be described, a main pressure leakage adaptive constant may be determined based on the engine speed at which point the main pressure for a hydraulic system reaches its regulation point. As this will be a factor dependent on the leakage of the system, it will be necessary for the controller <NUM> to learn and understand the leakage and restrictions of the system.

As previously described, engine speed may continue to increase even after main pressure regulates, and the main regulator valve directs the additional fluid to the converter circuit <NUM>, cooler circuit <NUM>, and lube circuit <NUM>. As lube pressure builds, it too regulates and the pressure switch <NUM> can detect this regulation point and send a signal to the controller <NUM> indicating this condition has been reached. In <FIG>, a graphical representation <NUM> is shown of lube pressure as a function of engine speed. Here, as engine speed increases, lube pressure also increases. A nominal curve <NUM> is shown as being indicative of a nominal or average hydraulic system. A first curve <NUM> and a second curve <NUM> are also shown where the nominal curve <NUM> is disposed therebetween. The first curve <NUM> may represent a hydraulic system with a minimum amount of leakage, and the second curve <NUM> may represent a hydraulic system with a maximum amount of leakage.

Lube pressure continues to increase as engine speed increases, and like main pressure, reaches its regulation point <NUM> at a defined engine speed. The nominal curve <NUM> reaches regulation at a nominal regulation point <NUM>. Similarly, the first curve <NUM> and second curve <NUM> reach regulation at a first regulation point <NUM> and a second regulation point <NUM>, respectively. As shown, each curve reaches the regulation pressure <NUM> at different engine speeds, thereby indicating a variance <NUM> in leakage adaptive. From this, a lube pressure leakage adaptive constant may be determined as a function of engine speed and the lube pressure regulation point for the given hydraulic system.

As shown in <FIG> and <FIG>, at a given set of conditions including engine speed and temperature, a lube regulator valve <NUM> and main regulator valve <NUM> will stroke to regulated positions for a nominal hydraulic system. Due to leakage and variation in each hydraulic system, however, both valves may stroke to their respective regulation positions at a different engine speed than the nominal system. For instance, if there is more leakage in one hydraulic system, it may take longer to build main and lube pressures and therefore the pressures may not regulate until at a higher engine speed. Alternatively, if there is less leakage, the main pressure and lube pressure may regulate quicker than the nominal system, and thus at a reduced engine speed. From the systems of <FIG> and <FIG>, the point at which lube pressure regulates can be detected and communicated to the controller <NUM>. As a result, the controller <NUM> can make necessary adjustments to pump flow and other outputs in the system to compensate for leakage and variance in the system. For purposes of this disclosure, this is called leakage adaptive.

The controller can learn a leakage adaptive constant for either or both main pressure and lube pressure. Once the leakage adaptive constant is known, particularly for lube pressure, the controller <NUM> can make the necessary adjustments to the system and predict flows and pressures of the system under most conditions. Moreover, once the lube circuit is satisfied and lube pressure regulates, additional fluid pumped by the variable displacement pump into the lube circuit <NUM> can be directed to sump <NUM>. Fluid pressure and flow can be controlled under different transient conditions, as well as fluid temperature can be controlled by adjusting pump flow.

The controller <NUM> can learn and store the different regulation points for each condition under which main pressure and/or lube pressure regulates (e.g., when ascending an incline, filling a clutch, cruise-like conditions, stop-and-go conditions, etc.). The controller <NUM> can create tables and store the regulation values based on temperature, speed, etc. As the same condition is repeated, the controller <NUM> can determine if main or lube pressure regulated at about the same point as done previously. In addition, the controller <NUM> can operably control the pump control solenoid <NUM> to command a certain flow characteristic or profile based on previously learned conditions. The controller <NUM> can also determine if the pressure switch <NUM>, <NUM> triggered a signal thereto based on regulation of lube pressure or main pressure. In the event the pressure has not regulated, the controller <NUM> can continuously adapt and relearn to changing conditions. While leakage may or may not vary under most circumstances, temperature variation may cause the greatest variation or change in leakage in the system. The controller <NUM> therefore can continuously learn and adapt to temperature variation and other changes in the hydraulic system.

Another aspect to leakage adaptive is prognostic control. For a given set of conditions, the leakage adaptive constant for either main pressure or lube pressure should generally not change substantially unless there is an issue in the hydraulic system. In <FIG>, for example, suppose the regulation point for lube pressure is <NUM> RPM for a certain condition (e.g., at a defined temperature, etc.). As the controller <NUM> continuously monitors when the pressure switch <NUM> detects movement of the lube regulator valve <NUM> to its regulated position, the controller <NUM> can further detect changes in the regulation point. For instance, if engine speed continuously increases before the regulation point is reached, the controller <NUM> may detect a problem in the hydraulic system. A broken seal or damage to the variable displacement pump may cause an increase in leakage in the system, thereby resulting in the lube pressure (or main pressure) regulation point changing with increasing engine speed.

In the event of a possible leakage induced by a broken seal or other problem in the hydraulic system, the controller <NUM> can be programmed or include instructions to detect the problem. For instance, the controller <NUM> can include instructions that indicate a threshold or threshold range. This threshold or range may be based on a specific engine speed at which lube or main pressure regulates. Alternatively, this threshold or range may be based off a degree of change in the regulation point. Moreover, this threshold or range may be based off how quickly the regulation point changes (i.e., a time-based consideration). The controller <NUM> may track the number of times the lube pressure or main pressure regulates and detect the change in regulation point based off a count or quantity of regulation detections. The pressure switch <NUM> provides an input to the controller <NUM> to detect when the lube pressure regulates and the second pressure switch <NUM> provides another input to the controller <NUM> for when main pressure regulates. Therefore, in the example above, if lube pressure suddenly regulates at <NUM> RPM rather than <NUM> RPM, the controller <NUM> can detect this and trigger an alarm or diagnostic code. Depending on the severity of the leak, the controller <NUM> may further limit the functionality of the transmission to prevent further damage to the transmission.

A further aspect of the present disclosure is the ability to characterize both the fluid flow and pressure throughout the entire hydraulic system. In this aspect, a model-based hydraulic control system can include a learning feature to better understand the leakage in any given transmission or hydraulic system so that the amount of fluid flow and pressure needed under any condition can be provided without substantial delay. More particularly, the controller can predetermine leakage in the hydraulic system, and based on the amount of leakage therein, control the output of the variable displacement pump to accurately provide fluid flow and pressure throughout the system under any condition. In doing so, the inherent time delay or response of the pump can be overcome by compensating for leakage and geometrical restrictions in the system. In this disclosure, the model-based approach can be referred to as a "feed forward" model.

As previously described, the combination of the pressure switches <NUM>, <NUM> and pump control solenoid <NUM> of <FIG> and <FIG> can allow the "feed forward" model to be incorporated into any given hydraulic system. Through the addition of the pump control solenoid <NUM>, the main "decrease" pressure leading to the decrease port of the pump can be accurately controlled such that, for example, if the controller predicts an upcoming shift, the controller <NUM> can controllably actuate the solenoid <NUM> to increase pump flow before a clutch fill command is initiated. In doing so, the increased pump flow before commanding a clutch fill can allow the hydraulic system to meet the demand of filling the clutch with a sufficient amount of fluid without de-stabilizing the system due to a lack of fluid supply and delayed time response of the pump. Moreover, many of the issues due to the undershoot and overshoot of fluid flow can be avoided via this approach.

In the proposed feed forward model, the controller can receive a plurality of inputs, such as engine or input speed, transmission range or gear ratio, and fluid temperature (at sump). Additional inputs can be received or calculated based on the leakage of the system. Once certain inputs are received by the controller, the controller can learn and/or predict the requirements for fluid flow and fluid pressure such that main pressure can be controlled via the main pressure solenoid <NUM> and fluid flow can be controlled by the pump control solenoid <NUM>. As a result, not only is the fluid supply accurately provided to fill clutches, for example, but the controller can also provide the accurate amount of fluid to the clutches and other locations in the hydraulic system to improve shift quality and leakage. This can reduce or remove excess fluid flow that otherwise may increase spin losses in the transmission.

The feed forward model is a characterization of the hydraulic system and monitoring various inputs and operating conditions so that flow and pressure requirements can be predicted and controlled accordingly. As described, this can be incorporated into a closed loop control system such that the controller can make adjustments to flow and pressure requirements based on changes to system leakage and the inputs. In other words, the controller can operate in accordance with the feed forward model by anticipating what various input values should be under a given set of conditions, and then if the actual input value deviates from its predicted value, the controller can continuously make adjustments to the estimated value in real-time rather than react under conventional circumstances.

To better understand the feed forward model approach, the controller can first learn and determine the leakage adaptive value for the particular hydraulic system. In <FIG>, an exemplary embodiment of a feed forward model is shown. Here, the controller (i.e., the transmission controller or control unit) is a provided a means for determining a leakage constant for the hydraulic system in the form of a flow model <NUM>. The flow model <NUM> considers leakage and geometrical restrictions in the different circuits that define the hydraulic system. For instance, the flow model <NUM> can characterize the leakage from a pump <NUM> and controls <NUM>. As shown, fluid is transferred from an output of the pump <NUM> to the controls <NUM>, which as described above can be part of the main circuit. From the controls <NUM>, fluid can be supplied to clutches <NUM>.

Once the main circuit is satisfied and main pressure regulates, fluid is supplied to the converter circuit <NUM>, cooler circuit <NUM>, and lube circuit <NUM>. Once the lube circuit <NUM> is satisfied and lube pressure regulates, any additional fluid can be exhausted or returned to sump <NUM> (i.e., labeled "Exhaust" in <FIG>). This excess fluid, which is shown by arrow <NUM> in <FIG>, can be referenced as "total unusable" fluid since the main circuit and lube circuit are satisfied. In one aspect, it can be desirable for the controller to control pump flow so as to minimize the amount of "total unusable" fluid to improve transmission performance. This can be controlled by controlling pump displacement via actuation of the pump control solenoid as previously described. In another aspect, the leakage adaptive parameter or pump leakage factor <NUM> can be calculated by the controller by removing this unusable quantity of fluid for a given set of conditions.

Once the controller determines that lube pressure has regulated, the controller can determine the leakage for the hydraulic system. As shown in <FIG>, the pump <NUM> can contribute to the overall system leakage by producing pump leakage "P" <NUM>. Moreover, there is controls leakage "C" <NUM>, and in addition, the clutches <NUM> contribute both bleeds "B"<NUM> and fill flow "F" <NUM>. The converter circuit <NUM>, cooler circuit <NUM>, and lube circuit <NUM> each contribute flow restrictions <NUM> based on geometry (e.g., orifice size, bleed diameters), converter type, and converter mode.

Referring to <FIG>, a plurality of information <NUM> in the form of tables can be downloaded and stored in the memory unit of the controller. In table <NUM>, for example, the controller can determine the restriction value for the converter circuit <NUM> based on the mode of which the torque converter is operating. For instance, the torque converter may include a lockup clutch such that the converter operates in either a converter mode or lockup mode.

In table <NUM>, the controller can retrieve individual restriction diameters for the converter circuit <NUM>, based on either converter mode or lockup mode, the cooler circuit <NUM>, and the lube circuit <NUM>. The summation of the restrictions of the converter circuit <NUM>, cooler circuit <NUM>, and lube circuit <NUM> can provide a total restriction value <NUM>.

In table <NUM>, the controller can retrieve bleed orifices for each clutch based on transmission range or gear ratio. The bleeds are generally necessary to facilitate the release or exhaust of air from the clutches. As shown in table <NUM>, the bleed orifice area values <NUM> are arranged based on the transmission range or gear ratio, and these values <NUM> can be derived from individual bleed diameters for each clutch in the transmission. The individual bleed diameters may be retrieved from table <NUM>. In one aspect, there may be two clutches engaged for a single range. From the individual bleed diameters, the bleed orifice area values <NUM> in table <NUM> can be determined. In a different aspect, there may be a different number of clutches engaged for a single range. For instance, it may be possible only clutch is engaged. Alternatively, three or more clutches may be engaged for a given range. In any event, the individual bleed diameters for each clutch can be used to determine the combined bleed orifice area <NUM> for each given range or gear ratio.

In table <NUM>, the controller can retrieve the controls leakage <NUM> for each given range or gear ratio. In one aspect, the values for the controls leakage <NUM> can be predetermined and stored in the memory unit of the controller, similar to the bleed orifice area values <NUM>. The controller can retrieve additional information from table <NUM>, including individual clutch fill flow <NUM> and fluid viscosity factors. Lastly, in table <NUM>, the controller can retrieve a pump displacement value and then determine the overall pump leakage factor <NUM>. In at least one aspect, the pump leakage factor <NUM> can be an overall summation of the leakage/fluid demands of each circuit or sub-system in the transmission.

To accommodate for the fluid viscosity, each of the tables in <FIG> may include different values dependent upon various temperatures or temperature ranges. For instance, one value may correspond to a fluid temperature within the range of <NUM> and <NUM>, whereas a different value may correspond to a fluid temperature within the range of <NUM> and <NUM>. There may be other variations in the values besides those based on fluid temperature, but fluid temperature does often impact fluid viscosity the greatest.

Pump leakage <NUM> can often be a big factor or component in the overall leakage in the hydraulic system. However, once the lube regulation point is known or determined, the controller can calculate the overall leakage of the system in accordance with the flow model of <FIG> and the tabular information <NUM> of <FIG>. The leakage adaptive parameter is based on pump speed (i.e., input speed), fluid temperature, clutch fill, and the like. Once these are known, the flow requirements of the system can be determined and fulfilled as needed.

To do so, the controller can use the leakage adaptive parameter or pump leakage factor to adjust pump displacement. This is achieved via the pump control solenoid, which as described above, can control the "decrease" pressure of the variable displacement pump. By controlling this "decrease" pressure, the pump displacement can either be increased or decreased. To better illustrate this process, reference is hereby made to <FIG>. In <FIG>, a control process is provided for controlling pressures and flow throughout the hydraulic system of the transmission. This process <NUM> illustrates several steps that are only intended to be exemplary, and not limiting. For instance, other methods may include more or less steps than that shown in <FIG>. As a result, the method or process of <FIG> is an exemplary embodiment that illustrates the overall process of regulating pressure within the different circuit or sub-systems of the transmission so that flows and pressures can be desirably determined based on future demand.

In <FIG>, a first step <NUM> is achieved by producing fluid flow in a hydraulic system of the transmission. Here, this is generally done by the variable displacement pump that can be integrally disposed within an outer housing of the transmission. However, as described above, alternative embodiments may include a second pump disposed before or after the cooler circuit to provide additional flow. Other embodiments may include a hydraulic pump disposed outside of the transmission to further facilitate fluid flow in the transmission. In this example, the variable displacement pump can produce fluid flow and pressure in the main circuit of the transmission.

In step <NUM>, the pressure in the main circuit, i.e., main pressure, can reach a regulation point. As shown in <FIG>, a pressure switch <NUM> can be disposed in communication with the main regulator valve <NUM> so that as main pressure regulates, the pressure switch <NUM> can send a signal along communication link <NUM> to the controller <NUM> to alert the controller <NUM> of this condition. Moreover, once main pressure regulates in step <NUM>, the main regulator valve <NUM> can stroke to its regulated position so that additional fluid can be directed to the converter circuit <NUM>, cooler circuit <NUM> and lube circuit <NUM> in step <NUM>.

As fluid pressure builds in the lube circuit <NUM>, the pressure, i.e., lube pressure, reaches a regulation point in step <NUM>. In doing so, the lube regulator valve <NUM> can stroke to its regulated position, thereby triggering the pressure switch <NUM> to detect this position and send a signal to the controller <NUM> along communication link <NUM>. At this point, the controller <NUM> has learned or determined the regulation point in the main circuit, lube circuit, or both (e.g., in the embodiment of <FIG>) in accordance with step <NUM>. Moreover, as described, the different pressure switches can detect these regulation points and communicate this information via signals to the controller <NUM> in step <NUM>.

In step <NUM>, the controller can determine a pump leakage adaptive factor based on the regulation points, and primarily based off the lube regulation point. As described above with reference to <FIG> and <FIG>, the controller can retrieve various inputs (e.g., controls leakage values, bleeds, restrictions, etc.). Many of these inputs will be dependent upon temperature, range, and converter mode. The controller can receive this type of information according to various known means, including those previously described. Once the controller has retrieved all of the input data, it can compute the pump leakage factor or leakage adaptive parameter.

As previously described, the leakage adaptive parameter is a leakage adjustment variable for the overall leakage in the transmission. Once the controller determines this parameter, it can input this value into a pump supply equation to determine flows and pressures throughout the hydraulic system. In one non-limiting aspect, a transmission with nominal hardware may have a leakage factor of <NUM>. If a transmission has more leakage than the nominal transmission, the leakage factor or parameter will likely adapt to a greater value, e.g., <NUM>. Likewise, if a transmission has less leakage than the nominal transmission, the leakage factor or parameter will likely adapt to a lesser value, e.g., <NUM>. This can be seen in <FIG>, for example, where the nominal transmission may have a leakage adaptive factor of <NUM> that reaches the lube pressure regulation point <NUM> at a lower engine speed than the "more leakage" transmission that may have a leakage adaptive factor of <NUM> and reaches its lube pressure regulation point <NUM> at a higher engine speed.

Therefore, a transmission that has more leakage will likely adapt to a higher leakage adaptive parameter compared to the nominal transmission, whereas the transmission that has less leakage will likely adapt to a lower leakage adaptive parameter. The leakage adaptive parameter, however, may change over time if there is additional leakage in the transmission. For instance, if the controller determines that the downstream pressure switch <NUM> toggles or moves earlier or later than expected, the leakage adaptive parameter will adjust accordingly. As a result, the controller can calculate the flow demands of the transmission under different conditions, and based on this feed forward model, the controller can then optimize the displacement of the variable displacement pump in step <NUM>. Moreover, as the controller calculates the flow demands of the transmission, the controller can operably control the output of the pump control solenoid to adjust pump displacement as needed.

In <FIG>, an exemplary graphical representation <NUM> is provided to illustrate how the control system can adjust pump flow based on flow demands during a shift. In <FIG>, an exemplary supply curve <NUM> and demand curve <NUM> are provided for a given set of conditions. As described above, there are various inputs necessary for determining flow requirements throughout the system. This includes engine speed, transmission sump temperature, main modulation state, transmission range, and whether a clutch is being filled. Based on these inputs, the controller can calculate the supply of fluid flow from the pump based on the following supply equation: <MAT> where NE is engine speed, PD is pump displacement, P is pressure, v is fluid viscosity, and K is a constant based on the leakage adaptive factors. K can be a function of pump leakage <NUM>, controls leakage <NUM>, and leakage due bleed holes <NUM>.

Moreover, the variable K can also be a function of range. The controller may have a lookup table stored in its memory in which K is adjusted by a correction factor on the basis of transmission range. For instance, if the transmission range is reverse, the variable K may be adjusted by a correction factor of <NUM>. Alternatively, if the transmission range is second, the variable K may be adjusted by a correction factor of <NUM>. Again, these correction factors can be predetermined and stored in the memory unit of the transmission controller.

In <FIG>, the supply curve <NUM> is shown as having a negative slope due in part to the leakage of the pump, controls, bleed orifices, seals, etc. In a perfect flow model without leakage, the pump flow would be substantially constant at any given speed, but the model as described in the present disclosure can accommodate for the various leakages in the system. The flow demand curve <NUM> is also shown. At one point <NUM> in <FIG>, the supply curve <NUM> and demand curve <NUM> intersect, thereby representing a certain pressure at which the flow demanded is the same as the flow being supplied. However, at another pressure represented by "P" in <FIG>, the supply flow QS is less than the demand flow QD (i.e., difference between points <NUM> and <NUM>). As shown, the pump flow <NUM> being supplied during the shift is insufficient to meet the flow demand <NUM> to fill the oncoming clutch during the shift. As such, the controller can calculate this demand for the clutch fill as follows: <MAT> where A is the area of the feed orifice in the clutch and ΔP is the difference between the pressure, P, and the return spring of the clutch. The controller therefore can determine both the fluid demand for filling the oncoming clutch and the fluid supply being output by the pump.

On the basis of the pump supply and flow demand equations above, the controller can adjust the pump supply to meet the flow demand by controllably adjusting the pump displacement as described in this disclosure. In other words, the controller can receive the necessary inputs as described above and retrieve constants and other variables for determining the leakage adaptive parameter. Based on transmission range and temperature, the controller can obtain viscosity (as a function of temperature) and correction factors to determine pump supply. Thus, if the controller determines that for a given pressure the pump supply is insufficient for the flow demand to fill an oncoming clutch, the controller can controllably adjust pump displacement until the supply flow meets the required demand flow. Stated another way, by adjusting pump displacement, the supply flow curve <NUM> in <FIG> can be moved vertically until the supply flow point <NUM> intersects with the demand flow point <NUM>. With the controller being able to adjust the supply flow to meet the flow demands during a shift, the controller can effectively improve shift quality and durability of the transmission.

Referring to <FIG>, the controller can also adjust the pump supply when the transmission is operating between shifts. Here, the controller can operate a closed loop control system by monitoring flow requirements to satisfy the lube circuit and maintain sump temperature at or near a desired temperature. To do so, the controller can determine how much pressure is needed to keep engaged clutches from slipping for a given amount of engine torque. The pressure can be regulated by the main regulator valve, as described above, to maintain clutch capacity. Once the controller has determined the requisite amount of pressure, any excess fluid supply can be directed to the converter, cooler circuit, and lube circuit.

The controller can be programmed to determine the amount of flow that is required to satisfy the requirements of the lube circuit. For instance, a plurality of flow requirement values may be provided in the form of a lookup table or graph. In <FIG>, an exemplary graphical representation <NUM> is provided for determining flow requirements to satisfy a lube circuit. Here, the flow requirements can be set forth on the basis of a transmission speed, i.e., input speed or output speed. The controller can receive or determine the input or output speed of the transmission, and based on this speed, retrieve the required flow requirement to meet the needs of the transmission lube circuit. In <FIG>, for example, a flow profile <NUM> is shown as a function of speed. The flow requirement increases as speed increases, but at a predetermined speed, N, the flow requirement can level off and remain substantially constant for increasing speeds. For instance, the predetermined speed, N, may refer to <NUM> RPM for the transmission output speed. At <NUM> RPM, the flow requirement, QL, is indicated by point <NUM> on the flow profile <NUM>. In this instance, if the controller determines that the output speed, N, is <NUM> RPM, the controller can retrieve the flow requirement value Q<NUM> from the graphical representation. If the speed is different, the controller can interpolate between values or pull a defined value from the flow profile <NUM>.

In addition, the controller can monitor the transmission sump temperature, and based on this temperature adjust flow through the cooler circuit. For instance, in <FIG> a different graphical representation <NUM> is shown of a flow profile <NUM> as a function of temperature change. The controller can continually monitor sump temperature in accordance with the methods described herein. Moreover, the controller can be preprogrammed or have a desired or threshold temperature stored in its memory unit. Alternatively, the sump temperature may be set by a vehicle operator, for example. In any event, the controller can be provided with a desired or threshold sump temperature and make adjustments to the hydraulic control system to change the sump temperature, as needed.

In <FIG>, a first temperature point <NUM> and a second temperature point <NUM> are shown along the flow profile <NUM>. In this embodiment, the first temperature point <NUM> corresponds to a difference between desired and actual temperature, ΔT<NUM>. The second temperature point <NUM> refers to a second difference, ΔT<NUM>. Each of the changes in temperature corresponds to a different flow. For instance, the first change in temperature ΔT<NUM> corresponds to a first flow requirement, Q<NUM>, and the second change in temperature ΔT<NUM> corresponds to a second flow requirement, Q<NUM>.

Based on the flow profile <NUM> of <FIG>, if the desired or threshold temperature is TT but the actual sump temperature is lower than the threshold, the controller may not adjust the supply flow. However, if the actual sump temperature is greater than the threshold temperature, the controller can determine the difference between the actual and threshold temperatures. Based on this difference, the controller can determine the flow requirement from the graphical representation <NUM> of <FIG> to reduce the sump temperature. This can be achieved by providing additional flow through the cooler circuit, as described above.

Moreover, as described above with reference to <FIG>, the controller can determine the corresponding pressure for maintaining clutch capacity at a certain engine torque. Alternatively, rather than engine torque, this may be a function of accelerator or throttle pedal position. In any event, the controller can determine the amount of fluid being supplied by the pump at the given pressure using the pump supply equation above.

This supply flow, QS, corresponds to the amount of flow available to satisfy the converter, cooler circuit and lube circuit. As described, the controller can then determine whether the supply flow, QS, is sufficient for satisfying lube, converter and cooling, and if not, the controller can then make adjustments to pump displacement to increase flow in the overall system. If, based on current input or output speed, the lube flow requirement, QL, is less than QS and the controller determines the sump temperature is at or less than the threshold temperature, TT, the controller can make further adjustments to reduce flow and provide better fuel economy.

On the other hand, if the lube flow requirement, QL, is greater than the supply flow, QS, the controller can controllably adjust pump displacement to increase the amount of fluid supplied by the pump to satisfy the needs of the lube circuit. In addition, if the actual sump temperature is greater than the temperature threshold, TT, the controller can compute this difference and use the graphical representation <NUM> of <FIG> to determine the amount of flow needed to reduce the sump temperature.

Referring to <FIG>, a graphical representation <NUM> is provided for a torque converter flow requirement. The torque converter can be a significant heat generator, particularly during instances in which the vehicle is ascending a steep grade or repeatedly launching from a stop. As described above with reference to <FIG>, torque multiplication occurs through the fluid coupling between the drive unit <NUM> and transmission <NUM> such that the turbine shaft <NUM> is exposed to more torque than is being supplied by the drive unit <NUM>. The torque multiplication is advantageous for transferring torque to the wheels during a vehicle launch, but it also tends to generate the most heat in the torque converter. As a result, it can be desirable to remove or dissipate this heat through the cooler circuit, if possible.

The transmission controller can be used to monitor the amount of heat being generated by the torque converter by monitoring the amount of torque produced by the drive unit (or engine) and detecting or calculating the amount of converter slip. Converter slip can be defined as the ratio of input speed and turbine speed. Stated another way, the converter slip is the speed differential across the torque converter. The controller can receive input torque from the engine or drive unit via a datalink or signal path between the controller and drive unit control circuit (e.g., engine controller). In the event the transmission controller cannot receive the input torque, the controller can calculate the input torque as a function of slip speed.

In <FIG>, a flow profile <NUM> is shown for satisfying a converter flow requirement. Here, the controller can calculate the converter slip speed and then retrieve a desired flow from the graphical representation <NUM> of <FIG>. For example, in <FIG>, there are a plurality of defined flows along the flow profile <NUM>, including a first flow Q<NUM> and a second flow Q<NUM>. The first flow, Q<NUM>, corresponds to point <NUM> on the flow profile <NUM> at a first slip speed, SS<NUM>. Similarly, the second flow, Q<NUM>, corresponds to point <NUM> on the flow profile <NUM> at a second slip speed, SS<NUM>. It is to be understood that both slip speed values are only two of a plurality of slip speed values. The controller may interpolate as necessary to determine the desired flow at a different slip speed value. Alternatively, the controller may be programmed with a formula for the flow profile based on slip speed or input torque. In any event, the controller can continuously monitor the slip speed and determine whether additional flow is needed to dissipate the heat generation from the torque converter.

In addition, while only one flow profile <NUM> is shown in <FIG>, there may be a plurality of flow profiles. Each flow profile may be related to a specific position of the accelerator pedal (i.e., throttle pedal position or percentage). Moreover, there may be various curves depending on the type and model of the torque converter. In the event the torque converter includes a lockup clutch, the controller can monitor or detect when the lockup clutch is engaged. When the lockup clutch is engaged, the controller can be programmed to skip the evaluation of the converter flow requirement and only determine the amount of flow required for the lube and cooler circuits.

Thus, on the basis of <FIG>, the controller can be programmed or instructed to evaluate three flow requirements, i.e., the lube requirement, sump temperature or cooler requirement, and converter flow requirement. In one aspect, the controller can determine which of the three flow requirements is the greatest, and based on this maximum flow, the controller can adjustably control pump displacement to achieve the desired amount of flow. In a different aspect, the controller may sum the three flow requirements, calculate the average, or compute a different desired flow on the basis of the three flow requirements. Moreover, the controller can continuously monitor, calculate, and determine the three flow requirements and make real-time adjustments to pump displacement based on changes to any of the requirements. By adjusting pump displacement, the controller can effectively control the three flow requirements as desired. In doing so, the controller can also improve overall fuel economy of the vehicle.

While the flow requirements for the lube circuit, cooler circuit, and converter are shown in <FIG>, and <FIG> as graphical representations, it is to be understood that these may lookup tables with values for the controller to retrieve. For the lube circuit, the flow required may be provided based on transmission input speed, turbine speed, transmission output speed, torque or shift frequency. Likewise, for the cooler circuit, the flow required to reduce sump temperature may be provided based on a plurality of temperature differences, e.g., in increments of <NUM>-<NUM>. Similarly, for the converter flow requirement, the flow required to dissipate heat generated in the converter may be provided based on slip speed, input torque, converter model, and/or accelerator pedal position. Once the controller determines the supply flow and the required flow to satisfy each of the requirements of the lube circuit, cooler circuit and converter circuit, the controller can controllably actuate the pump control solenoid to adjust pump displacement. Moreover, this can be part of a closed-loop control where the controller can continuously calculate and determine the flow supply and flow demand of the system and continuously adjust pump displacement to improve fuel economy.

Claim 1:
A hydraulic system (<NUM>) of an automatic transmission for controlling fluid flow through the automatic transmission, comprising:
a controller (<NUM>) for operably controlling the system (<NUM>, <NUM>);
a variable displacement pump (<NUM>) adapted to be driven by a torque-generating mechanism, the pump (<NUM>) having an inlet and an outlet, where the pump (<NUM>) is configured to generate fluid flow and pressure throughout the system;
a main circuit (<NUM>) fluidly coupled to the pump (<NUM>), the main circuit (<NUM>) adapted to operate and control the transmission;
a solenoid (<NUM>) disposed in electrical communication with the controller (<NUM>), the solenoid (<NUM>) controllably coupled to the pump (<NUM>) to alter the displacement of the pump (<NUM>);
a first circuit (<NUM>) fluidly coupled to the outlet of the pump (<NUM>);
a regulator valve (<NUM>) disposed in fluid communication with the main circuit (<NUM>), the regulator valve (<NUM>) being configured to move between a regulated position and an unregulated position, where the regulated position corresponds to a regulated pressure in the main circuit (<NUM>);
a pressure switch (<NUM>) fluidly coupled to the regulator valve (<NUM>) and configured to move between a first position and a second position, wherein the pressure switch (<NUM>) is disposed in electrical communication (<NUM>) with the controller (<NUM>) to regulate pump flow of the variable displacement pump (<NUM>);
a second circuit (<NUM>) fluidly coupled to the pump (<NUM>), the second circuit (<NUM>) operably controlled to adjust a temperature of the fluid in the system, wherein a fluid flow through the second circuit (<NUM>) is adjusted by the altered displacement of the pump (<NUM>) based on the temperature of the fluid;
a temperature sensor (<NUM>) disposed in electrical communication (<NUM>) with the controller (<NUM>), the temperature sensor (<NUM>) adapted to detect the temperature of the fluid; and
a plurality of flow paths in the system, the plurality of flow paths comprising at least a first flow path (<NUM>) defined between the outlet of the pump (<NUM>) and the regulator valve (<NUM>), a second flow path (<NUM>) defined between the regulator valve (<NUM>) and the main circuit (<NUM>), and a third flow path (<NUM>, <NUM>) defined between the regulator valve (<NUM>) and the second circuit (<NUM>),
wherein fluid passed through the third flow path (<NUM>, <NUM>) flows into the first circuit (<NUM>).