Continuously variable transmissions (CVT) and transmissions that are substantially continuously variable are increasingly gaining acceptance in various applications. The process of controlling the ratio provided by the CVT is complicated by the continuously variable or minute gradations in ratio presented by the CVT. Furthermore, the range of ratios that are available to be implemented in a CVT are not sufficient for some applications. A transmission is capable of implementing a combination of a CVT with one or more additional CVT stages, one or more fixed ratio range splitters, or some combination thereof in order to extend the range of available ratios. The combination of a CVT with one or more additional stages further complicates the ratio control process, as the transmission will have multiple configurations that achieve the same final drive ratio.
The different transmission configurations could for example, multiply input torque across the different transmission stages in different manners to achieve the same final drive ratio. However, some configurations provide more flexibility or better efficiency than other configurations providing the same final drive ratio.
Hybrid and electric vehicles typically recover kinetic energy through a regenerative braking process. Friction brakes can be sized/downsized based on the assumption that the battery will have storage capacity for the energy that is recovered. Should that storage capacity be unavailable, the base braking system may be inadequate or overheat. A method is needed to dissipate excess energy in the scenario where the battery is full, faulted, temperature limited, or otherwise compromised.
Provided herein is a vehicle including: an engine; a first motor/generator; a second motor/generator; a variator; and a controller configured to detect an energy dissipation mode of operation; and wherein the controller commands a change in the variator ratio based on the energy dissipation mode.
Provided herein is a method for controlling an electric hybrid vehicle having an engine, a first motor/generator, a second motor/generator, and a variator, the method including the steps of: receiving a plurality of data signals provided by sensors located on the transmission, the plurality of data signals including: a variator ratio, a motor/generator temperature, a motor/generator speed, a battery temperature, and a battery power; detecting an energy dissipation condition based on the data signals; determining a regenerative brake torque request; determining a variator torque dissipation request; determining a variator ratio command based on the regenerative brake torque request and the variator torque dissipation request; and commanding the variator to operate at the target variator ratio.
All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.
Novel features of the preferred embodiments are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present embodiments will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the devices are utilized, and the accompanying drawings of which:
An electronic controller is described herein that enables electronic control over a variable ratio transmission having a continuously variable ratio portion, such as a Continuously Variable Transmission (CVT), Infinitely Variable Transmission (IVT), or variator. The electronic controller could be configured to receive input signals indicative of parameters associated with an engine coupled to the transmission. The parameters could include throttle position sensor values, accelerator pedal position sensor values, vehicle speed, gear selector position, user-selectable mode configurations, and the like, or some combination thereof. The electronic controller could also receive one or more control inputs. The electronic controller could determine an active range and an active variator mode based on the input signals and control inputs. The electronic controller could control a final drive ratio of the variable ratio transmission by controlling one or more electronic actuators and/or solenoids that control the ratios of one or more portions of the variable ratio transmission.
In some embodiments, the electronic controller described herein is described in the context of a continuous variable transmission, such as the continuous variable transmission of the type described in U.S. patent application Ser. No. 14/425,842, entitled “3-Mode Front Wheel Drive And Rear Wheel Drive Continuously Variable Planetary Transmission” and, U.S. patent application Ser. No. 15/572,288, entitled “Control Method of Synchronous Shifting of a Multi-Range Transmission Comprising a Continuously Variable Planetary Mechanism”, each assigned to the assignee of the present application and hereby incorporated by reference herein in its entirety. However, the electronic controller is not limited to controlling a particular type of transmission but rather, is optionally configured to control any of several types of variable ratio transmissions.
Some embodiments disclosed herein are related to the control of a variator and/or a CVT using generally spherical planets each having a tiltable axis of rotation that is adjustable to achieve a desired ratio of input speed to output speed during operation. In some embodiments, adjustment of said axis of rotation involves angular misalignment of the planet axis in a first plane in order to achieve an angular adjustment of the planet axis in a second plane that is substantially perpendicular to the first plane, thereby adjusting the speed ratio of the variator. The angular misalignment in the first plane is referred to here as “skew”, “skew angle”, and/or “skew condition”. In one embodiment, a control system coordinates the use of a skew angle to generate forces between certain contacting components in the variator that will tilt the planet axis of rotation. The tilting of the planet axis of rotation adjusts the speed ratio of the variator.
As used here, the terms “operationally connected”, “operationally coupled”, “operationally linked”, “operably connected”, “operably coupled”, “operably coupleable”, “operably linked,” and like terms, refer to a relationship (mechanical, linkage, coupling, etc.) between elements whereby operation of one element results in a corresponding, following, or simultaneous operation or actuation of a second element. It is noted that in using said terms to describe inventive embodiments, specific structures or mechanisms that link or couple the elements are typically described. However, unless otherwise specifically stated, when one of said terms is used, the term indicates that the actual linkage or coupling will take a variety of forms, which in certain instances will be readily apparent to a person of ordinary skill in the relevant technology.
For description purposes, the term “radial”, as used herein indicates a direction or position that is perpendicular relative to a longitudinal axis of a transmission or variator. The term “axial” as used herein refers to a direction or position along an axis that is parallel to a main or longitudinal axis of a transmission or variator.
It should be noted that reference herein to “traction” does not exclude applications where the dominant or exclusive mode of power transfer is through “friction”. Without attempting to establish a categorical difference between traction and friction drives herein, generally, these are understood as different regimes of power transfer. Traction drives usually involve the transfer of power between two elements by shear forces in a thin fluid layer trapped between the elements. The fluids used in these applications usually exhibit traction coefficients greater than conventional mineral oils. The traction coefficient (μ) represents the maximum available traction forces that would be available at the interfaces of the contacting components and is a measure of the maximum available drive torque.
Typically, friction drives generally relate to transferring power between two elements by frictional forces between the elements. For the purposes of this disclosure, it should be understood that the CVTs described here could operate in both tractive and frictional applications. As a general matter, the traction coefficient μ is a function of the traction fluid properties, the normal force at the contact area, and the velocity of the traction fluid in the contact area, among other things. For a given traction fluid, the traction coefficient μ increases with increasing relative velocities of components, until the traction coefficient μ reaches a maximum capacity after which the traction coefficient μ decays. The condition of exceeding the maximum capacity of the traction fluid is often referred to as “gross slip condition”. Traction fluid is also influenced by entrainment speed of the fluid and temperature at the contact patch, for example, the traction coefficient is generally highest near zero speed and decays as a weak function of speed. The traction coefficient often improves with increasing temperature until a point at which the traction coefficient rapidly degrades.
As used herein, “creep”, “ratio droop”, or “slip” is the discrete local motion of a body relative to another and is exemplified by the relative velocities of rolling contact components such as the mechanism described herein. In traction drives, the transfer of power from a driving element to a driven element via a traction interface requires creep. Usually, creep in the direction of power transfer, is referred to as “creep in the rolling direction.” Sometimes the driving and driven elements experience creep in a direction orthogonal to the power transfer direction, in such a case this component of creep is referred to as “transverse creep.”
Those of skill will recognize that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein, including with reference to the transmission control system described herein, for example, could be implemented as electronic hardware, software stored on a computer readable medium and executable by a processor, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described herein generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans could implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present embodiments. For example, various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein could be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor could be a microprocessor, but in the alternative, the processor could be any conventional processor, controller, microcontroller, or state machine. A processor could also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Software associated with such modules could reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other suitable form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor reads information from, and write information to, the storage medium. In the alternative, the storage medium could be integral to the processor. The processor and the storage medium could reside in an ASIC. For example, in one embodiment, a controller for use of control of the CVT includes a processor (not shown).
Referring now to
Referring now to
Provided herein is a control method where the variator is intentionally operated in an inefficient manner to purposefully dissipate excess kinetic energy. In some embodiments having a ball-type CVP or other traction type transmission such as a toroidal type of transmission, kinetic energy is dissipated through the contact patch between contacting components of the respective transmissions.
Provided herein is a braking control algorithm that generates an energy dissipation request from a braking request and available regen and friction brake capacities.
Provided herein is a braking control algorithm that specifically requests a variator ratio command targeted towards a suboptimal variator efficiency region.
Provided herein is a braking control algorithm that monitors variator fluid temperature to prevent overheating the transmission during energy dissipation mode.
Provided herein is a braking control algorithm that monitors electric motor temperature to enable energy dissipation mode.
Provided herein is a braking control algorithm that monitors battery temperature to enable energy dissipation mode.
Provided herein is a braking control algorithm that monitors battery power limits to enable energy dissipation mode.
Turning now to
In some embodiments, the variator 24 is similar to the variator described in
In some embodiments, the variator 24 is similar to the variator described in
In other embodiments, the variator 24 is similar to the variator described in
The electric hybrid powertrain 20 has a planetary gear set 25 having a ring gear 26 operably coupled to the second motor/generator 23, a planet carrier 27 operably coupled to the engine 21, and a sun gear 28 operably coupled to the first motor/generator 21.
In some embodiments, the second motor/generator 23 is operably coupled to the variator 24. The variator 24 is configured to transmit an output power to a final drive gear 29. It should be appreciated that a variety of configuration for coupling the variator 24 to the second motor/generator 23 are known. As illustrative example, electric hybrid powertrains are disclosed in U.S. patent Ser. No. 15/760,653; 15/760,647; and Ser. No. 15/774,628, which are hereby incorporated by reference.
Referring now to
Turning now to
Referring now to
In some embodiments, the signals include a battery power limit, a battery temperature, and a brake torque request. The energy dissipation control process 130 proceeds to a block 133 where a regenerative braking control algorithm generates a braking torque request based on the signals received. The energy dissipation control process 130 proceeds to a block 134 where a variator torque dissipation request is determined based on the brake torque request and available torque capacity of other elements in the powertrain. For example, the variator torque dissipation request is determined from the following expressions: Tdissipation=Tbrake_request−Tregen_cap−Tfriction_cap; where Tdissipation is the variator torque dissipation request, Tbrake_request is the brake torque request, Tregen_cap is the regeneration torque capacity of the powertrain, Tfriction_cap is the friction torque capacity in the powertrain. The energy dissipation control process 130 proceeds to a block 135 where limits on the energy dissipation request due to fluid temperature or other thermal factors are applied. The energy dissipation control process 130 proceeds to a block 136 where an energy dissipation error is calculated using the expressions Error=Tdissipation−Tdissipation_est, where Tdissipation is the variator torque dissipation request, and Tdissipation_est is the estimated variator energy dissipation, which is calculated in the block 138. The energy dissipation control process 130 proceeds to a block 137 where a variator ratio command is determined based on the calculated error.
In some embodiments, the variator ratio command moves the variator to a suboptimal operating region in terms of variator efficiency. The energy dissipation control process 130 proceeds to a block 138 where energy loss in the variator is estimated using a variator efficiency model programmed in the hybrid supervisory controller 200.
In some embodiments, the variator efficiency model is based on the input speed, input torque, and the variator ratio. The energy dissipation control process 130 proceeds to a block a block 139 where commands are sent to adjust the variator to the variator ratio command determined in the block 137. It should be appreciated, that the energy dissipation control process 130 runs in a loop while enabled and is disabled when the entry criteria from process 120 are no longer met.
Provided herein are configurations of CVTs based on a ball-type variator, also known as CVP, for continuously variable planetary. Basic concepts of a ball-type Continuously Variable Transmissions are described in U.S. Pat. Nos. 8,469,856 and 8,870,711 incorporated herein by reference in their entirety. Such a CVT, adapted herein as described throughout this specification, comprises a number of balls (planets, spheres) 1, depending on the application, two ring (disc) assemblies with a conical surface contact with the balls, as input traction ring assembly 2 and output traction ring assembly 3, and an idler (sun) assembly 4 as shown on
The working principle of such a CVP of
Referring now to
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The foregoing description details certain embodiments. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the preferred embodiments are practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the preferred embodiments should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the preferred embodiments with which that terminology is associated.
While preferred embodiments have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the preferred embodiments. It should be understood that various alternatives to the preferred embodiments described herein could be employed in practicing the preferred embodiments. It is intended that the following claims define the scope of the preferred embodiments and that methods and structures within the scope of these claims and their equivalents be covered thereby.
The present application claims priority to U.S. Provisional patent application Ser. No. 62/538,195, filed on Jul. 28, 2017, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62538195 | Jul 2017 | US |