Brake reduction using gearbox control

Abstract

Braking system for a machine (10) with a power source (18) having a power source output shaft (36), a transmission (20) having a transmission input shaft (38), a torque converter (50) operatively connected to the power source output shaft (36) and the transmission input shaft (38), and a lock-up clutch (LUC) (58) operatively connected to the power source output shaft (36) and the transmission input shaft (38) and having an unlocked LUC position in which the power source output shaft (36) and the transmission input shaft (38) can rotate freely relative to each other, and an unlocked LUC position in which the power source output shaft (36) and the transmission input shaft (38) are locked together to rotate together, wherein the braking system comprises: a brake input device (26); a braking force device (46) which exerts a braking force in response to the displacement of the brake input device (26) in order to reduce the machine travel speed of the machine (10); a brake input device position sensor (72) which is operatively connected to the brake input device (26) to detect the displacement of the brake input device (26) and to transmit signals relating to the displacement of the brake input device, with displacement values ​​corresponding to a detected extent of the displacement of the brake input device (26); a speed sensor (74, 76, 78, 80) which is operatively connected to a component of the machine (10) to detect a speed of the component which indicates a current machine travel speed, and to transmit machine travel speed signals with speed values ​​corresponding to the current machine travel speed; and an electronic control module (ECM) (30) which is operatively connected to the LUC (58), the brake input device position sensor (72) and the speed sensor (74, 76, 78, 80), wherein the ECM (30) is programmed to: to detect a displacement of the brake input device (26) based on the displacement values ​​in the signals relating to the displacement of the brake input device from the brake input device position sensor (72), to determine the current machine travel speed of the machine (10) on the basis of the rotational speed values ​​in the machine travel speed signals from the rotational speed sensor (74, 76, 78, 80), to compare a combination of the shift of the brake input device and the current machine travel speed with a transmission downshift scheme for the transmission (20) stored in a memory (62) associated with the ECM (30), to determine, based on a comparison of the combination of the brake input device displacement and the current machine speed with the transmission downshift scheme, whether the combination of the brake input device displacement and the current machine speed causes the transmission (20) to downshift, and to transmit LUC control signals to the LUC (58) to cause the LUC (58) to move into the unlocked LUC position when the combination of the displacement of the brake input device and the current machine travel speed causes the transmission (20) to downshift.

Description

Technical field

[0001] The present disclosure relates generally to braking in vehicles and machines, and in particular to a torque converter and a controllable lock-up clutch that are integrated into a braking strategy for a vehicle or machine to reduce the use and overheating of the vehicle's or machine's brakes. background

[0002] Working machines, such as wheel loaders, include a drivetrain to power traction devices like wheels, tracks, and the like, to move the machine across a work surface. In a typical drivetrain configuration, a power source, such as an internal combustion engine, is operatively connected to an automatic transmission via a torque converter. The transmission, in turn, is operatively connected to an axle that rotates the traction devices to move the machine across the work surface. The automatic transmission is connected to the power source via a torque converter, which replaces the manual clutch of a manual transmission. The torque converter is a fluid coupling that allows the power source to be operated at low speeds, such as when the power source is idling, without being fluidly coupled to the transmission.At higher rotational speeds of the power source, which generate higher fluid pressure within the torque converter, the pressurized fluid drives the transmission and transfers the rotational power from the power source to the rotating load formed by the transmission, thus driving the transmission and traction devices to propel the machine. The torque converter may include a lock-up clutch that can be locked so that a power source output shaft and a transmission input shaft rotate at the same speed, and unlocked or disengaged to allow the shafts to rotate at different speeds. An example of a torque converter and lock-up clutch arrangement is disclosed in US Patent 4,961,484 A, granted to Kato et al. on October 9, 1990, entitled "Brake Device for a Vehicle."

[0003] Furthermore, DE 199 53 587 B4 discloses a vehicle lock-up clutch control system. In a vehicle equipped with an internal combustion engine and an electric motor as interchangeable drive sources, a torque converter attached to the vehicle transmission is controlled to utilize the advantages of the electric motor when it is used as the drive source. A characteristic map used to determine whether the lock-up clutch should be engaged is selected according to whether the drive source is the internal combustion engine, the internal combustion engine plus engine-generator, or the engine-generator.

[0004] Furthermore, US 2014 / 0200113A1 teaches a coasting downshift control device for an automatic transmission. Under a specific condition, where a torque converter is held in a locked state to extend the fuel cut-off time, a downshift command is generated due to the vehicle coasting with an accelerator pedal position of APO=0, whereupon an automatic transmission downshifts by a drop in hydraulic pressure P. off on the release side of the clutch and an increase in hydraulic pressure P on On the engagement side of the clutch, this causes a downshift followed by re-engagement. During the re-engagement of the downshift, the hydraulic pressure P onThe hydraulic pressure of the clutch on the engagement side is reduced from high when the lock is engaged to low when the lock is disengaged, after the time at which the release of the lock is predicted, thereby preventing a tendency to draw in the transmission output torque that may occur at the beginning of the inertia phase and also reducing the width of a subsequent change in vehicle deceleration G.

[0005] Present machines also include braking force devices that apply braking forces to components such as the axle on which the traction devices are mounted. The braking force exerts braking force on these components in response to an operator moving a brake input device within an operator station on the machine. The braking force reduces the machine's travel speed over the work surface, eventually to the point where the transmission downshifts to a lower gear. In these arrangements, the lock-up clutch disengages, if necessary, shortly after the movement of the brake input device is detected, and the drivetrain delivers a minimal deceleration force to the machine during braking due to slippage in the torque converter.As a result, the braking force device provides the majority of the machine's deceleration, so the braking force devices and the machine's components involved are subject to wear and heat generation associated with braking the machine.

[0006] The present invention is aimed at overcoming one or more of the problems or disadvantages associated with the prior art. Summary of Revelation

[0007] The object of the present invention is achieved by a braking system for a machine, a machine itself, and a method for controlling the engagement of a lock-up clutch of a torque converter to assist in braking and deceleration of a machine, according to the independent claims. The dependent claims relate to preferred embodiments of the invention.

[0008] According to one aspect of the present disclosure, a machine is disclosed. The machine comprises a power source with a power source output shaft, a transmission with a transmission input shaft and a transmission output shaft, a torque converter operatively connected to the power source output shaft and the transmission input shaft, and a lock-up clutch (LUC) operatively connected to the torque converter. The LUC has an unlocked position in which the power source output shaft and the transmission input shaft can rotate freely relative to each other, and a locked position in which the power source output shaft and the transmission input shaft are locked to rotate together. The machine further comprises a brake input device, a brake force device that exerts a brake force in response to the displacement of the brake input device,to reduce the machine's travel speed, a brake input device position sensor, which is operatively connected to the brake input device to detect the displacement of the brake input device and to transmit signals regarding the displacement of the brake input device with displacement values ​​corresponding to a detected displacement range of the brake input device, a transmission output speed sensor, which is operatively connected to the transmission output shaft to detect a current transmission output speed and to transmit transmission output speed signals with speed values ​​corresponding to the current transmission output speed, and an electronic control module (ECM), which is operatively connected to the LUC, the brake input device position sensor, and the transmission output speed sensor. The ECM is programmed toto detect a brake input device displacement based on the displacement values ​​in the brake input device displacement signals from the brake input device position sensor, to determine the current machine travel speed based on the speed values ​​in the transmission output speed signals from the transmission output speed sensor, to compare a combination of the brake input device displacement and the current machine travel speed with a transmission downshift scheme for the transmission stored in a memory associated with the ECM, and to determine, based on the comparison of the combination of the brake input device displacement and the current machine travel speed with the transmission downshift scheme, whether the combination of the brake input device displacement and the current machine travel speed causes the transmission to downshift.and to transmit LUC control signals to the LUC to cause the LUC to move into the unlocked LUC position when the combination of the brake input device displacement and the current machine travel speed causes the transmission to downshift.

[0009] According to a further aspect of the present disclosure, a method for controlling the engagement of a lock-up clutch (LUC) of a torque converter for assisting braking to decelerate a machine is disclosed. The torque converter is operatively connected to a power source output shaft of a power source and a transmission input shaft of a transmission, and the LUC is connected to the impeller and the turbine and has an unlocked LUC position in which the power source output shaft and the transmission input shaft can rotate freely relative to each other, and a locked LUC position in which the power source output shaft and the transmission input shaft are locked to rotate together.The procedure includes detecting a displacement of the brake input device of a brake input device, determining a current machine travel speed of the machine, comparing a combination of the current machine travel speed and the displacement of the brake input device with a transmission downshift scheme for the transmission, determining whether the combination of the displacement of the brake input device and the current machine travel speed causes the transmission to downshift, based on the comparison of the combination with the transmission downshift scheme, and causing the LUC to move into the unlocked LUC position if the combination of the displacement of the brake input device and the current machine travel speed causes the transmission to downshift.

[0010] According to another aspect of the present disclosure, a braking system for a machine is disclosed. The machine comprises a power source with a power source output shaft, a transmission with a transmission input shaft, a torque converter operatively connected to the power source output shaft and the transmission input shaft, and a lock-up clutch (LUC) operatively connected to the torque converter. The LUC has an unlocked position in which the power source output shaft and the transmission input shaft can rotate freely relative to each other, and a locked position in which the power source output shaft and the transmission input shaft are locked to rotate together. The machine further comprises a brake input device and a brake force device that exerts a braking force in response to the displacement of the brake input device in order to reduce the machine's travel speed.a brake input device position sensor, which is operatively connected to the brake input device to detect the displacement of the brake input device and to transmit signals relating to the displacement of the brake input device with displacement values ​​corresponding to a detected displacement range of the brake input device; a speed sensor, which is operatively connected to a component of the machine to detect a rotational speed of the component, which indicates a current machine travel speed, and to transmit machine travel speed signals with rotational speed values ​​corresponding to the current machine travel speed; and an electronic control module (ECM), which is operatively connected to the LUC, the brake input device position sensor, and the transmission output speed sensor. The ECM is programmed toto detect a displacement of the brake input device based on the displacement values ​​in the signals relating to the displacement of the brake input device from the brake input device position sensor, to determine the current machine travel speed of the machine based on the rotational speed values ​​in the machine travel speed signals from the rotational speed sensor, to compare a combination of the displacement of the brake input device and the current machine travel speed with a transmission downshift scheme for the transmission stored in a memory associated with the ECM, to determine, based on the comparison of the combination of the displacement of the brake input device and the current machine travel speed with the transmission downshift scheme, whether the combination of the displacement of the brake input device and the current machine travel speed causes the transmission to downshift,and to transmit LUC control signals to the LUC to cause the LUC to move into the unlocked LUC position when the combination of the brake input device displacement and the current machine travel speed causes the transmission to downshift.

[0011] Additional aspects of the invention are defined by the claims of this patent. Brief description of the drawings Fig. Figure 1 is a side view of an exemplary vehicle or machine capable of driving over a work surface; Fig. Figure 2 is a schematic illustration of a drive train of the vehicle or machine of Fig. 1, which includes a torque converter; Fig. Figure 3 is a schematic view of the electrical and control components of the vehicle or machine. Fig. 1; and Fig. Figure 4 is a graph of the shift of the brake input device versus the transmission output speed / vehicle speed with an exemplary transmission downshift scheme of a transmission of the vehicle or machine of Fig. 1; and Fig. Figure 5 is a block diagram of a routine for brake reduction and transmission control in accordance with the present disclosure, which is implemented by an electronic control module of the vehicle or machine. Fig. 1 can be executed. Detailed description

[0012] Fig. Figure 1 shows an exemplary vehicle or machine 10 in the form of a wheel loader capable of moving across a work surface at a work site. While a wheel loader is shown here, the brake reduction and transmission control strategy described herein can be implemented in any suitable type of work vehicle or machine capable of moving across a work surface. The machine 10 comprises a frame 12 supporting a machine body 14, the frame 12 being supported above the work surface by traction devices 16. As illustrated, the traction devices 16 include a plurality of wheels, but the traction devices 16 could be any other suitable devices, such as an undercarriage with tracks, half-tracks, or combinations of tracks, wheels, or other traction devices.

[0013] The machine 10 is driven by a drivetrain comprising a power source 18, such as a motor, operatively connected to a gearbox 20, which in turn is operatively connected to the wheels 16. The gearbox 20 transmits power generated by the motor 18 to the wheels 16 to rotate the wheels 16 and move the machine 10 across the work surface. The gearbox 20 can be any automatic transmission with a series of gears and clutches (not shown), the clutches selectively engaging the gears to achieve a variety of forward and reverse gears with appropriate gear ratios to provide a range of speed and torque outputs necessary for the machine 10 to move across the work surface and perform work functions.

[0014] An operator can control the movement of the machine 10, along with other operations of the machine 10, at an operator station 22. The controlled operations can include speed control, braking, steering, unloading, actuation of work attachments of the machine 10, and the like. The operator station 22 can have a variety of operator input devices 24 for inputting commands for the engine 18, the transmission 20, and other systems of the machine 10. The operator input devices 24 can include engine throttles, brake pedals 26, gearshift levers, steering wheels 28, work attachment lifting and steering controls, graphical user interfaces, and the like.Sensors assigned to each of the operator input devices 24 detect manipulation of the operator input devices 24 by an operator and transmit corresponding input device sensor signals, which are received and processed by an electronic control module (ECM) 30. Of particular relevance to the present disclosure are brake input device sensor signals, which are transmitted by a displacement sensor of the brake input device when a brake input device, such as the brake pedal 26, is moved to cause a braking force to be applied to reduce the travel speed of the machine 10. The brake input device sensor signals can be evaluated by the ECM 30 to determine when brake assistance by the powertrain can and should be applied according to the brake reduction and transmission control strategy, which will be explained in detail below.

[0015] The machine 10 also collects and records operational data relating to its operation as it works within the work area and moves across the work surface. The machine 10 can include a number of sensors 32, which can operate independently or as components of other control and monitoring systems, to automatically monitor various operational data as the machine 10 moves across the work surface and the performance of the machine operations within the work area. The sensors 32 that monitor the operational data can include speed sensors that detect machine, motor, and gearbox speeds, as well as torque sensors that detect the torque at various points along the drive train and / or the rolling resistance of the wheels 16. Some operational data can be monitored directly, while other data can be derived or calculated from the monitored parameters.

[0016] Fig. Figure 2 shows a schematic illustration of the drive train of the machine 10 from the motor 18 to the wheels 16. The motor 18 may include a rotational energy storage device, such as a flywheel 34, and a power source output shaft 36 extending away from it. The transmission 20 comprises a transmission input shaft 38 at one input end and a transmission output shaft 40 at one output end. The forward and reverse gears of the transmission 20 have corresponding gear ratios for transmitting the input speed and input torque to the transmission input shaft 38 as a desired output speed and output torque to the transmission output shaft 40. The transmission output shaft 40 may, in turn, be operatively connected to a differential 42, which transmits the transmission output torque to an axle 44 that is operatively connected to and drives the wheels 16.One or more braking force devices 46 are connected to the axle 44, the wheels 16, or other moving components of the drive train. The braking force devices 46 can be selectively actuated by the operator in response to the displacement of the brake input device 26 to exert a braking force to decelerate the wheels 16 and, consequently, the machine's travel speed. In some implementations, the braking force devices 46 are operatively connected to the brake input device 26 by a mechanical linkage or a cable, so that the displacement of the brake input device 26 is converted into a corresponding movement of the braking force devices 46.In a hydraulic brake system, the brake input device 26 is operatively connected to a brake cylinder, such that the displacement of the brake input device 26 increases the pressure in the brake cylinder to move a piston and thereby engage the brake force devices 46. The brake force devices 46 can alternatively or additionally be controlled by the ECM 30, for example in an anti-lock braking system.

[0017] As in Fig. As shown in Figure 2, the machine 10 includes a torque converter 50, which allows the motor 18 to operate at low engine speeds, such as when the motor 18 is idling, without being fluidically coupled to the transmission 20. At higher engine speeds, which generate a greater fluid pressure within the torque converter 50, the torque converter 50 acts as a fluid coupling with the transmission 20, transmitting the rotational power from the motor 18 to the rotating driven load formed by the transmission, in order to drive the transmission and the wheels to propel the machine.

[0018] The torque converter 50 comprises, as shown, an impeller 52, a turbine 54, and a stator 56. The impeller 52 can be oriented as shown in the diagram of Fig. 2 shown in conjunction with and rotating at the same speed as the associated power source output shaft 36. The turbine 54 is operatively connected to the transmission input shaft 38, so that the transmission input shaft 38 can rotate in conjunction with and at the same speed as the turbine 54. The rotation of the impeller 52 can generate a hydrodynamic fluid coupling within the torque converter 50 and accordingly rotate the turbine 54 and the transmission input shaft 38. The stator 56 can be arranged between the impeller 52 and the turbine 54 and can, if necessary, positively and efficiently modify the fluid flow between the impeller 52 and the turbine 54 during the operation of the machine 10.The stator 56 is fixed in position relative to the impeller 52 and the turbine 54 as illustrated, but in alternative embodiments it can be fixed in one direction and rotatable in the opposite direction, or be provided with a stator coupling that can be selectively engaged to alternately fix the stator 56 in its position or release the stator 56 to be freely rotatable.

[0019] The torque converter further comprises a lock-up clutch 58, which can be operatively connected between the impeller 52 and the turbine 54. The lock-up clutch 58 is actuated to selectively engage and lock the impeller 52 and the turbine 54 from rotating together. The lock-up clutch 58 can be in an unlocked position, or LUC (Load-Free Clutch) position, for example, during vehicle acceleration when a speed difference between the impeller 52 and the turbine 54 is desired. Conversely, the lock-up clutch 58 can be in a locked LUC position to physically lock the impeller 52 and the turbine 54 when they are rotating at nearly the same speed, for example, when the vehicle is coasting at a constant speed. This effectively transforms the torque converter 50 into a purely mechanical clutch with no slippage and greater efficiency, without the hydraulic losses associated with hydrodynamic coupling.

[0020] The operator input devices 24, the ECM 30, and the sensors 32 are components of a machine control system for the machine 10. With reference to Fig. Figure 3 shows an exemplary arrangement of electrical and control components of the drive train of machine 10, with various control components integrated into the braking system. The ECM 30 can process the information received from the operator input devices 24 and the sensors 32 using software stored in the ECM 30 and output command and control signals to the motor 18 and the actuators of machine 10. The ECM 30 can include a microprocessor 60 for executing a specific program that controls and monitors various functions assigned to machine 10.The processor 60 can be operatively connected to a memory 62, which may include a read-only memory (ROM) 64 for storing programs and a random access memory (RAM) 66, which serves as a working memory area for use in the execution of a program stored in the ROM 64. The memory 62 is illustrated here as integrated into the ECM 30, but it will be clear to those skilled in the art that the memory 62 can be provided separately from the ECM 30 but on board machine 10, and / or remotely from the ECM 30 and machine 10, while still being associated with and accessible through the ECM 30 for storing information in it and retrieving it from the memory 62, as is necessary during the operation of the machine 10.Although the processor 60 is shown, it is also possible and considered to use other electronic components such as a microcontroller, an ASIC chip (application-specific integrated circuit), or any other integrated circuit device. While the explanation herein relates to the functionality of a drivetrain control system, the ECM 30 can be configured to control other aspects of the operation of the machine 10, such as steering, unloading material loads, actuating work attachments, and the like. Furthermore, the ECM 30 can refer to multiple control and processing units through which the functionality of the drivetrain control system and other systems of the machine 10 can be distributed. For example, the operator station 22, the motor 18, and a braking system can each have one or more ECMs that communicate with the main ECM 30.Such variations in the composition and distribution of the processing of the ECM 30, as described herein, are being considered for use in brake reduction and transmission control in accordance with the present disclosure.

[0021] The operator input devices 24 have corresponding sensor devices that detect input actions by the operator and are operatively connected to the ECM 30 to transmit sensor signals with values ​​corresponding to the operator's input. The sensor devices transmit sensor signals to the ECM 30 in response to the operator manipulating the operator input devices 24 in the operator station 22. Relevant to the present disclosure is that the sensor devices detect the displacement of control elements such as the accelerator pedal or brake pedal 26 and transmit sensor signals with values ​​corresponding to the extent of the displacement of the operator input device 24.The sensor signals can be used by the ECM 30 to control the corresponding components or systems of the machine 10, such as the motor 18 or the braking system, or to perform further processing relating to the operation and control of other components and systems that depend on operator inputs, such as the control of the gearbox 20 and the lock-up clutch 58, as will be explained in more detail below.

[0022] The sensors for the operator input devices 24 can include a speed input device position sensor 70, which is operatively connected to a speed input device, such as an accelerator pedal, a joystick, or another type of speed control device that can be manipulated by the operator to indicate the desire to increase or decrease the travel speed and / or the power of the machine 10. The speed input device position sensor 70 detects the degree of displacement of the speed input device and transmits speed input device displacement signals to the ECM 30 with values ​​corresponding to the displacement of the speed input device.The sensors for the operator input devices 24 may further include a brake input device position sensor 72, which is operatively connected to a brake input device such as a brake pedal 26 or another input device that can be manipulated by the operator to cause a braking force to be applied in order to reduce the travel speed of the machine 10. Similar to the speed input device position sensor 70, the brake input device position sensor 72 detects an extent of displacement of the brake input device and transmits signals regarding the displacement of the brake input device to the ECM 30, with values ​​corresponding to the displacement of the brake input device.

[0023] The sensors 32 can include sensors that provide information about the current operating state of the drive train of the machine 10. In general, such sensors 32 can include speed, torque, and position sensors that transmit signals corresponding to the speeds, loads, and angular positions of various rotating components of the machine 10. Component speed sensors are particularly relevant for the present brake reduction and transmission control strategy. Consequently, the ECM 30 can be operatively connected to a power source output speed sensor 74, a transmission input speed sensor 76, a transmission output speed sensor 78, and an axle speed sensor 80, among other speed sensing devices.The power source output speed sensor 74 is operatively connected to the power source output shaft 36 and transmits power source output speed signals with values ​​indicating the speed of the power source output shaft 36 and the impeller 52. The transmission input speed sensor 76 is operatively connected to the transmission input shaft 38 and transmits transmission input speed signals with values ​​indicating the speed of the transmission input shaft 38 and the turbine 54. The transmission output speed sensor 78 is operatively connected to the transmission output shaft 40 and transmits transmission output speed signals with values ​​indicating the speed of the transmission output shaft 40. The axle speed sensor 80 is operatively connected to the axle 44 and transmits axle speed signals with values ​​indicating the speed of the axle 44 and the wheels 16.

[0024] The ECM 30 is also operatively connected to various output and control devices, which can be operational and controllable elements of the machine 10, in addition to other machine functions for locomotion and braking, controlled based on information from the operator input devices 24 and the sensors 32. The output and control devices include a motor controller 82. The motor controller 82 can be integrated into the motor 18 and can be a mechanical controller, an electronic controller implemented in software, or another suitable conventional motor output control mechanism and corresponding control strategy.As illustrated, the motor controller 82 can receive power source control signals from the ECM 30 to cause the motor controller 82 to increase, decrease, or maintain the motor output speed and / or power as dictated by the speed input device displacement signals from the speed input device position sensor 70. In alternative embodiments, the motor controller 82 can have a separate ECM and receive the speed input device displacement signals directly from the speed input device position sensor 70 and process the signals to control the motor 18. In other embodiments, a mechanical motor controller 82 can be operatively connected to the speed input device via a linkage, cable, or other connection mechanism to respond directly to manipulation of the speed input device by the operator.

[0025] The transmission 20 comprises one or more transmission actuators 84 that engage and disengage the clutches of the transmission 20 to shift between the available gears and corresponding gear ratios, while the engine output speed of the engine 18 and the travel speed of the machine 10 increase and decrease in response to the operator's manipulation of the speed input device. A transmission upshift scheme can be stored in the memory 62 and be accessible to the ECM 30 to determine when to upshift from one gear to the next higher gear at the appropriate time to maximize the performance of the machine 10. The transmission upshift scheme can include sections for each upshift operation performed by the transmission 20 (1-2, 2-3, 3-4, etc.).The ECM 30 can use inputs such as the motor output speed from the power source output speed sensor 74, the transmission output speed from the transmission output speed sensor 78, or the axle speed from the axle speed sensor 80, from which the machine travel speed can be derived, in conjunction with the transmission upshift scheme, to determine when to shift up to the next gear. A transmission downshift scheme can be stored in memory 62 and used by the ECM 30 to determine when to downshift from one gear to the next appropriate lower gear. The transmission downshift scheme can also include sections for each downshift operation, and the ECM 30 can use similar detected speeds to determine when to transmit control signals to the transmission actuators 84 to perform the downshift operation.The ECM 30 can also use the brake input device displacement from the brake input device position sensor 72 to determine when to instruct the transmission actuators 84 to perform the downshift operation. The transmission downshift scheme is further explained below in conjunction with the brake reduction and transmission control strategy of this disclosure.

[0026] A lock-up clutch actuator 86, such as an electronic clutch pressure control or ECPC valve, controls the locking and unlocking of the locking clutch 58. An ECPC valve is only one example, and the lock-up clutch 58 can, of course, be controlled by any other suitable clutch actuator mechanism. The ECM 30 is programmed as part of the brake reduction and transmission control strategy to transmit LUC control signals to the LUC actuator 86 to move the lock-up clutch 58 between the locked and unlocked LUC positions.When the machine 10 subsequently reaches a free rolling speed and the ECM 30 determines that the impeller 52 and the turbine 54 are rotating at approximately the same speed, the ECM 30 can transmit LUC control signals to the LUC actuator 86 to move the lock-up clutch 58 into the locked LUC position for direct drive of the gearbox input shaft 38 by the power source output shaft 36. If operating conditions indicate that high torque loads are being experienced or are expected, or if other factors exist that cause the machine 10 to slow down, the ECM 30 transmits LUC control signals to the LUC actuator 86 to disengage the lock-up clutch 58. Such conditions may include factors located outside or inside the machine 10, for example, if the operator causes a movement of the brake input device 26 to slow the machine 10 down.The response of the ECM 30 to the displacement of the brake input device 26, in order to cause the LUC actuator 86 to disengage the lock-up clutch 58 as part of the brake reduction and transmission control strategy, will be explained below.

[0027] There are several strategies for determining when to downshift an automatic transmission. One example is provided in US 6,269,295 B1, granted to Gaugush et al. on July 31, 2001, entitled "Method and Apparatus for Transmission Control During Braking." The patent granted to Gaugush et al. teaches aspects of a transmission downshift scheme that evaluates the brake pedal position, machine speed, engine output speed, current gear, and lowest operating gear to determine whether to downshift. However, the reference document does not explain how to determine when a lock-up clutch may be engaged or disengaged during the operation of a machine or vehicle.

[0028] Fig. Figure 4 represents a graph 100 showing a section of an exemplary transmission downshift scheme for machine 10, used in an alternative downshift strategy. The x-axis of graph 100 represents the displacement of the brake input device expressed as a percentage of a maximum displacement of the brake input device. The y-axis represents the transmission output speed (TOS) in revolutions per minute and / or the machine travel speed in kilometers per hour. A first line 102 on graph 100 represents a section of the transmission downshift scheme for downshifting from third gear to second gear, and a second line 104 represents a section of the transmission downshift scheme for downshifting from fourth gear to third gear. Lines 102 and 104 are purely exemplary, and graph 100 of the transmission downshift scheme 100 may vary based on operational requirements for a specific machine 10.

[0029] Generally, for a given gear, a downshift occurs when the combination of the current displacement of the brake input device and the current machine speed crosses the corresponding line 102, 104 from above to below. Using line 104 for fourth gear as an example, if the brake input device 26 is not displaced, a downshift is performed when the transmission output speed drops below 1,200 rpm and / or the machine speed drops below 16.8 km / h (10.44 mph). If the brake input device 26 is displaced, the transmission output speed or the machine speed initially remains the same. Consequently, no downshift occurs at any point above and to the left of line 104.Point 108 lies within a dead zone of the brake actuation below a minimum displacement line of the brake input device 110, where the brake input device 26 is indeed displaced, but the brake force devices 46 do not yet exert any braking force on the axle 44 and / or the wheels 16. A second point 112 lies outside the dead zone, but the machine 10 has not yet slowed the transmission output speed or machine travel speed sufficiently to trigger a downshift to third gear.

[0030] As the displacement of the brake input device and the braking force increase, the transmission output speed and the machine travel speed decrease until the combination intersects line 104 at a point, approximately point 114. At point 114, the ECM 30 determines that downshifting to third gear should occur and transmits control signals to the transmission actuator 84 to cause the transmission clutches to shift the transmission 20 into third gear. Depending on the sampling rate of sensors 74, 76, 78, 80, the deceleration rate of the machine 10, and the speed at which the operator actuates the brake input device 26, the ECM 30 may not determine that downshifting should occur until a combination such as point 116, located to the right and below line 104, is reached.At this point, the ECM 30 transmits transmission control signals to cause the transmission actuators 84 to downshift the transmission 20 to third gear, and then begins to evaluate the shift of the brake input device and the transmission output speed and machine travel speed against the section of the transmission downshift scheme for third gear represented by line 102. The person skilled in the art will recognize that the downshift strategies described herein do not address the locking and unlocking of lock-up clutches in torque converters, into which the brake reduction and transmission control strategy can be integrated in accordance with the present disclosure. Commercial applicability

[0031] In currently known machines, the brake force devices 46 provide the majority of the braking force for decelerating the machine 10 when the brake input device 26 is displaced. The torque converter 50 allows relative rotation between the power source output shaft 36 and the transmission input shaft 38, so that the drive train contributes only a minimal deceleration force to slow the machine 10. Even when the lock-up clutch 58 is engaged, current machines 10 are designed to disengage the lock-up clutch 58 after a relatively small displacement of the brake input device 26. In some earlier implementations, the lock-up clutch 58 disengages after a predetermined displacement of the brake input device, regardless of the machine's travel speed, the engine output speed, the transmission output speed, or the current transmission ratio.With the lock-up clutch 58 released, using the brake force devices 46 solely to engage the axle 44 and / or the wheels 16 can lead to overheating or premature failure of the components.

[0032] In a brake reduction and transmission control strategy in accordance with the present disclosure, the drivetrain is used to assist the deceleration of the machine 10 when the operator moves the brake input device 26 by keeping the lock-up clutch 58 engaged until operating conditions indicate that the transmission 20 will downshift. This allows the drivetrain to remain in direct drive for a longer period and provide increased deceleration, which reduces wear and heat generation on the brake force devices 46, the axle 44, and the wheels 16. Braking performance is improved because the service brakes are assisted by the drivetrain, and less heat is transferred to the axle 44, thereby extending the service life of the axle 44.

[0033] Fig. Figure 5 is a flowchart for a LUC release routine 120, which can be stored in memory 62 and executed by the ECM 30 to control the release of the locking clutch 58 when the operator moves the brake input device 26 to reduce the machine travel speed of the machine 10. The routine 120 can use the movement of the brake input device, the machine travel speed, and a transmission downshift scheme, such as the one described above, or similar schemes, to determine an optimal time to release the locking clutch 58 so that the transmission can exert a deceleration force for at least one time period to assist the brake force devices 46 and reduce the friction and heat generated by the brake components. The routine 120 can begin at block 122, where the ECM 30 determines whether the locking clutch 58 is locked.As previously explained, the ECM 30 can transmit LUC control signals to the LUC actuator 86 to lock the bypass clutch 58 when the gearbox input speed is approximately equal to the power source output speed. The ECM 30 can maintain a LUC status indicating whether the bypass clutch 58 is locked or unlocked, or it can determine the current state of the bypass clutch 58 during the execution of routine 120. If, at block 122, the ECM 30 determines that the bypass clutch 58 is unlocked, the control can return to the start of routine 120 until the bypass clutch 58 is locked for direct drive of the gearbox 20. It will be clear to those skilled in the art that the comparison at block 122 can be omitted, and the ECM 30 can continuously perform the processing described below while the machine 10 is in operation.

[0034] If the ECM 30 determines at block 122 that the bypass clutch 58 is locked, or if block 122 is not present, the control system switches to block 124, where the ECM 30 evaluates the brake input device movement signals from the brake input device position sensor 72 to determine whether the operator is moving the brake input device 26. If the brake input device movement signals do not indicate any movement, the operator is not requesting braking force to decelerate the machine 10. In this case, the control system can return to block 124 to continue monitoring the brake input device movement signals for operator input.If the ECM 30 determines at block 124 that the brake input device 26 is being moved by the operator, the control can proceed to a block 126 in which the ECM 30 can determine whether the signals regarding the displacement of the brake input device indicate that the brake input device 26 has been moved by more than a predetermined minimum displacement. In some implementations, it may not be necessary or desirable to disengage the bypass clutch 58 if the displacement of the brake input device 26 is only within the dead zone to the left of line 110 in graph 100. Fig. 4, and the braking force devices 46 are not yet exerting any friction to slow down the machine 10. Consequently, the ECM 30 can return control to block 124 if such a minimal displacement of the brake input device 26 is generated by the operator. Depending on the implementation, block 124 and the initial displacement detection can be omitted, and a single step can be performed to compare any displacement of the brake input device 26 with the minimum displacement of the brake input device.

[0035] If the ECM 30 at block 126 determines that the displacement of the brake input device 26 is greater than the minimum displacement of the brake input device, the control can transfer to a block 128 where the ECM 30 determines an actual gear of the transmission 20. As above with respect to the transmission downshift scheme, graph 100 of Fig. As explained in section 4, each downshift from a higher gear to a lower gear has a different downshift pattern, such as those represented, for example, by lines 102 and 104. The ECM 30 determines the current gear ratio, or gear, so that the correct portion of the gear downshift pattern can be used to decide whether to disengage the lock-up clutch 58. The current gear ratio can be stored in a searchable data structure within memory 62 when the ECM 30 performs an upshift or downshift.In implementations where the ECM 30 is a brake ECM 30 specifically intended for the braking system of the machine 10, and a separate ECM 30 can control the transmission 20, the ECMs 30 can be configured to transmit the current transmission ratio to the brake ECM 30 when a transmission shift operation occurs, or the current transmission ratio can be retrieved by the brake ECM 30 from the transmission ECM 30 during the execution of block 128.

[0036] After determining the current gear ratio at block 128, the control system moves to block 130, where the ECM 30 determines the current machine travel speed of machine 10. The ECM 30 can use suitable sensor signals to derive the current machine travel speed. For example, the ECM 30 can use the gearbox output speed from the gearbox output speed signals and convert it from revolutions per minute to kilometers per hour, as shown on the Y-axis of graph 100. Alternatively, the axle speed from the axle speed signals from the axle speed sensor 80 and a wheel diameter of the wheels 16 can be used to calculate the current machine travel speed.

[0037] Using the current gear ratio and machine speed, determined at blocks 128 and 130 respectively, and the brake input device displacement known from the brake input device displacement signals, the control system can proceed to block 132. Here, the current machine speed and brake input device displacement are compared with the gear downshift scheme to determine whether a downshift will occur. In the exemplary gear downshift scheme of Fig. As explained above, a downshift occurs when the combination of the brake input device displacement and the machine travel speed lies on line 104 for fourth gear, for example, around point 114, or to the right and below line 104, such as point 116. The transmission downshift scheme, according to the specific strategy implemented in machine 10, can be stored in memory 62 as a map, an assignment field, or another searchable data structure containing brake input device displacements and machine travel speeds corresponding to lines 102 and 104.

[0038] The ECM 30 can be programmed to scan the map for the current brake input device offset. If the current brake input device offset is found in the transmission downshift scheme section for the current gear, a downshift occurs when the current machine speed is less than or equal to the machine speed corresponding to the brake input device offset. If the current brake input device offset is not found on the transmission downshift scheme map, the ECM 30 can use and interpolate the map entries on either side of the current brake input device offset to derive the machine speed at which the transmission downshift should occur, and similarly compare the derived machine speed to the current machine speed.Of course, the ECM 30 could be programmed to search the transmission downshift map according to the current machine speed, compare the corresponding brake input device offset with the current brake input device offset, and determine that the transmission downshift occurs when the current brake input device offset is greater than or equal to the brake input device offset from the transmission downshift map. Further alternative methods for comparison at block 132 can be implemented, if necessary, based on the downshift strategy and transmission downshift scheme implemented in machine 10, and such comparisons are considered in strategies in accordance with the present disclosure.

[0039] After the comparison at block 132 has been performed, the control system moves to block 134, where the ECM 30 determines whether the machine 10 is at a downshift point. If the comparison indicates that the combination of the current machine speed and the current displacement of the brake input device to the left above the corresponding line 102, 104 of the transmission downshift scheme, such as at points 108, 112 in Fig.When the combination is at position 4, downshifting does not yet occur, and the direct drive of the locked lock-up clutch 58 can be maintained to assist in decelerating the machine 10. Before downshifting the transmission, the control can move back to block 124 to continue monitoring the shift of the brake input device. When the combination is at position 102, 104 (point 114) or to the right below position 102, 104 (point 116), the machine 10 is at a downshift point, and the control can move to block 136, where the ECM 30 can transmit LUC control signals to the LUC actuator 86 to disengage or release the lock-up clutch 58, allowing the power source output shaft 36 and the transmission input shaft 38 to rotate at different speeds.

[0040] Keeping the lock-up clutch 58 locked for as long as possible in the brake reduction and transmission control strategy is optimal in order to supply a deceleration force to the machine 10 and thereby reduce wear on the brake force devices 46 and the heat transferred to the axle 44 and / or the wheels 16. However, if the lock-up clutch 58 is locked when the transmission downshifts, the direct drive can result in an abrupt shift with strong deceleration or jerking, which can be unpleasant for the operator of the machine 10.The brake reduction and transmission control strategy, in accordance with the present disclosure, eliminates this jerking and the disadvantages for the operator by identifying the optimal time to disengage the lock-up clutch 58 in order to maximize deceleration support from the drivetrain while ensuring a smooth downshift, i.e., at the same time as the transmission downshifts. Disengaging the lock-up clutch 58 generally requires less time than downshifting the transmission, so the lock-up clutch 58 is consistently and reliably disengaged before the lower gear is engaged.

Claims

[1] Braking system for a machine (10) comprising a power source (18) with a power source output shaft (36), a transmission (20) with a transmission input shaft (38), a torque converter (50) operatively connected to the power source output shaft (36) and the transmission input shaft (38), and a lock-up clutch (LUC) (58) operatively connected to the power source output shaft (36) and the transmission input shaft (38) and having an unlocked LUC position in which the power source output shaft (36) and the transmission input shaft (38) can rotate freely relative to each other, and an unlocked LUC position in which the power source output shaft (36) and the transmission input shaft (38) are locked together to rotate together, wherein the braking system comprises: a brake input device (26); a braking force device (46) which exerts a braking force in response to the displacement of the brake input device (26) in order to reduce the machine travel speed of the machine (10); a brake input device position sensor (72) which is operatively connected to the brake input device (26) to detect the displacement of the brake input device (26) and to transmit signals relating to the displacement of the brake input device, with displacement values ​​corresponding to a detected extent of the displacement of the brake input device (26); a speed sensor (74, 76, 78, 80) which is operatively connected to a component of the machine (10) to detect a speed of the component which indicates a current machine travel speed, and to transmit machine travel speed signals with speed values ​​corresponding to the current machine travel speed; and an electronic control module (ECM) (30) which is operatively connected to the LUC (58), the brake input device position sensor (72) and the speed sensor (74, 76, 78, 80), wherein the ECM (30) is programmed to: to detect a displacement of the brake input device (26) based on the displacement values ​​in the signals relating to the displacement of the brake input device from the brake input device position sensor (72), to determine the current machine travel speed of the machine (10) on the basis of the rotational speed values ​​in the machine travel speed signals from the rotational speed sensor (74, 76, 78, 80), to compare a combination of the shift of the brake input device and the current machine travel speed with a transmission downshift scheme for the transmission (20) stored in a memory (62) associated with the ECM (30), to determine, based on a comparison of the combination of the brake input device displacement and the current machine speed with the transmission downshift scheme, whether the combination of the brake input device displacement and the current machine speed causes the transmission (20) to downshift, and to transmit LUC control signals to the LUC (58) to cause the LUC (58) to move into the unlocked LUC position when the combination of the displacement of the brake input device and the current machine travel speed causes the transmission (20) to downshift. [2] Braking system according to claim 1, wherein the ECM (30) is programmed to determine whether the transmission (20) downshifts when the combination of the displacement of the brake input device and the current machine travel speed is within the transmission downshift scheme. [3] Braking system according to claim 1, wherein the ECM (30) is programmed to determine that the transmission (20) downshifts when the current machine speed is within the transmission downshift scheme and the shift of the brake input device is greater than a shift scheme shift of the brake input device corresponding to the current machine speed. [4] Braking system according to claim 1, wherein the ECM (30) is programmed to determine that the transmission (20) downshifts when the shift of the brake input device is within the transmission downshift scheme and the actual machine travel speed is less than a shift scheme machine travel speed corresponding to the shift of the brake input device. [5] Braking system according to claim 1, wherein the speed sensor (74, 76, 78, 80) is a transmission output speed sensor (78) which is operatively connected to a transmission output shaft (40) of the transmission (20) to detect a current transmission output speed and to transmit transmission output speed signals which have speed values ​​corresponding to the current transmission output speed, wherein the ECM (30) is programmed to determine the current machine travel speed on the basis of the speed values ​​in the transmission output speed signals. [6] Brake system according to claim 1, wherein the ECM (30) is programmed: to compare the displacement of the brake input device with a minimal displacement of the brake input device; and to determine whether the combination of the brake input device displacement and the current machine travel speed causes the transmission to downshift when the brake input device displacement is greater than the minimum brake input device displacement. [7] Braking system according to claim 1, wherein the transmission (20) has a plurality of transmission ratios for transmitting torque from the transmission input shaft (38) to a transmission output shaft (40) of the transmission (20), and wherein the ECM (30) is programmed to: to determine a current ratio of the multitude of transmission ratios of the gearbox (20); to determine a section of the transmission downshift scheme that corresponds to the current ratio of the multitude of transmission ratios of the transmission (20); to compare the combination of the current machine speed and the shift of the brake input device with the section of the transmission downshift scheme for the current ratio of the multitude of gear ratios; and to determine, on the basis of comparing the combination of the displacement of the brake input device and the current machine speed with the section of the transmission downshift scheme for the current ratio of the multitude of transmission ratios, whether the combination of the displacement of the brake input device and the current machine speed causes the transmission (20) to downshift. [8] Machine (10) comprising the following: a power source (18) with a power source output shaft (36); a gearbox (20) with a gearbox input shaft (38) and a gearbox output shaft (40); a torque converter (50) which is operatively connected to the power source output shaft (36) and the transmission input shaft (38); a lock-up clutch (LUC) (58) operatively connected to the torque converter (50), wherein the LUC (58) has an unlocked LUC position in which the power source output shaft (36) and the transmission input shaft (38) can rotate freely relative to each other, and a locked LUC position in which the power source output shaft (36) and the transmission input shaft (38) are locked together to rotate together; and the braking system according to claim 1, wherein the speed sensor (78) is operatively connected to the transmission output shaft (40). [9] Method for controlling the engagement of a lock-up clutch (LUC) (58) of a torque converter (50) for assisting braking to decelerate a machine (10), wherein the torque converter (50) is operatively connected to a power source output shaft (36) of a power source (18) and a transmission input shaft (38) of a transmission (20), and wherein the LUC (58) is operatively connected to the power source output shaft (36) and the transmission input shaft (38) and has an unlocked LUC position in which the power source output shaft (36) and the transmission input shaft (38) can rotate freely relative to each other, and a locked LUC position in which the power source output shaft (36) and the transmission input shaft (38) are locked to rotate together, the method comprising: Detection of a displacement of the brake input device of a brake input device (26); Determining the current machine speed of the machine (10); Comparing a combination of the current machine travel speed and the shift of the brake input device with a transmission downshift scheme for the gearbox (20); Determine whether the combination of the brake input device displacement and the current machine travel speed causes the transmission (20) to downshift, based on a comparison of the combination with the transmission downshift scheme; and Causing the LUC (58) to move into the unlocked LUC position when the combination of the displacement of the brake input device and the current machine travel speed causes the transmission (20) to downshift. [10] Method according to claim 9, comprising determining whether the transmission (20) downshifts when the combination of the displacement of the brake input device and the current machine travel speed is within the transmission downshift scheme. [11] Method according to claim 9, comprising determining that the transmission (20) downshifts when the current machine speed is within the transmission downshift scheme and the shift of the brake input device is greater than a shift scheme shift of the brake input device corresponding to the current machine speed. [12] Method according to claim 9, comprising determining that the transmission (20) downshifts when the displacement of the brake input device is within the transmission downshift scheme and the actual machine travel speed is less than a shift scheme machine travel speed corresponding to the displacement of the brake input device. [13] Method according to claim 9, wherein determining the current machine travel speed of the machine (10) comprises: Detecting a gearbox output speed of a gearbox output shaft (40) of the gearbox (20); and Converting the gearbox output speed into the current machine travel speed. [14] The method of claim 9, comprising: Comparing the displacement of the brake input device with a minimum displacement of the brake input device; and Determine whether the combination of the brake input device displacement and the current machine travel speed causes the transmission (20) to downshift when the brake input device displacement is greater than the minimum brake input device displacement. [15] Method according to claim 9, wherein the transmission (20) has a plurality of transmission ratios, and wherein comparing the combination of the current machine travel speed and the shift of the brake input device with the transmission downshift scheme and determining whether the combination causes the transmission (20) to downshift, comprises: Determining a current ratio of the multitude of gear ratios of the transmission (20); Determining a section of the transmission downshift scheme corresponding to the current ratio of the multitude of transmission ratios of the transmission (20); Comparing the combination of the current machine speed and the shift of the brake input device with the section of the transmission downshift scheme for the current ratio of the multitude of gear ratios; and Determine whether the combination of the brake input device displacement and the current machine travel speed causes the transmission (20) to downshift, based on a comparison of the combination of the brake input device displacement and the current machine travel speed with the transmission downshift scheme.

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