WO2018128848A1

WO2018128848A1 - Method for control of a continuously variable drive having a ball planetary type continuously variable transmission

Info

Publication number: WO2018128848A1
Application number: PCT/US2017/067854
Authority: WO
Inventors: Jeffrey M. DAVID; T. Neil MCLEMORE
Original assignee: Dana Limited
Priority date: 2017-01-03
Filing date: 2017-12-21
Publication date: 2018-07-12
Also published as: WO2018128829A1; WO2018128848A9

Abstract

Provided herein is a control system and method for a multiple-mode continuously variable transmission having a ball planetary variator. The control system has a transmission control module configured to receive a plurality of electronic input signals, and to determine a mode of operation from a plurality of control ranges based at least in part on the plurality of electronic input signals. The transmission control module includes a CVP control module and a clutch control module. The transmission control module is configured to control the speed ratio of the CVP based at least in part on the speed ratio of the CVD.

Description

METHOD FOR CONTROL OF A CONTINUOUSLY VARIABLE DRIVE HAVING A BALL PLANETARY TYPE CONTINUOUSLY VARIABLE

TRANSMISSION

RELATED APPLICATION

The present application claims the benefit of U.S. Provisional

Application No. 62/441 ,731 and U.S. Provisional Application No. 62/441 ,721 filed on January 3, 2017, which are incorporated herein by reference in its entirety.

BACKGROUND

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 can 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.

Previously described ratio control schemes for ball-type continuously variable transmissions operate almost exclusively in the CVP reference frame. There is a need for improved ratio control schemes for the more complex powerpaths or modular powerpaths that have an additional CVD reference frame enabling an additional layer of control stability as well as several new diagnostic functions.

SUMMARY

Provided herein is a method for controlling a continuously variable drive

(CVD) having a ball-planetary variator (CVP) provided with a ball in contact with a first traction ring assembly, a second traction ring assembly, and an idler assembly, wherein the CVP is operably coupled to a multiple speed gear box, 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 vehicle speed, a current CVD speed ratio, and a current CVP speed ratio; determining a commanded CVP speed ratio based at least in part on the current CVD speed ratio; and issuing the commanded CVP speed ratio to impart a change in operating condition of the CVD.

INCORPORATION BY REFERENCE

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

Figure 1 is a side sectional view of a ball-type variator.

Figure 2 is a plan view of a carrier member that used in the variator of Figure 1. Figure 3 is an illustrative view of different tilt positions of the ball-type variator of Figure 1. Figure 4 is a block diagram schematic of a vehicle control system that can be implemented in a vehicle.

Figure 5 is a schematic diagram of an exemplary continuously variable drive configured to be controlled by the vehicle control system of Figure 4.

Figure 6 is a table depicting the operating modes of the continuously variable drive of Figure 5.

Figure 7 is a block diagram depicting a continuously variable drive speed ratio control process implementable in the vehicle control system of Figure 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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 can be configured to receive input signals indicative of parameters associated with an engine coupled to the transmission. The parameters can 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 can also receive one or more control inputs. The electronic controller can determine an active range and an active variator mode based on the input signals and control inputs. The electronic controller can 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.

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 Number 14/425,842, entitled "3-Mode Front Wheel Drive And Rear Wheel Drive Continuously Variable Planetary Transmission" and, U.S. Patent Application Number 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.

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 United States Patent No. 8,469,856 and 8,870,711 incorporated herein by reference in their entirety. Such a CVT, adapted herein as described throughout this specification, includes 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 (first) traction ring assembly 2 and output (second) traction ring assembly 3, and an idler (sun) assembly 4 as shown on FIG. . In some embodiments, the output traction ring assembly 3 includes an axial force generator mechanism. The balls are mounted on tiltable axles 5, themselves held in a carrier (stator, cage) assembly having a first carrier member 6 operably coupled to a second carrier member 7. The first carrier member 6 rotates with respect to the second carrier member 7, and vice versa. In some embodiments, the first carrier member 6 is substantially fixed from rotation while the second carrier member 7 is configured to rotate with respect to the first carrier member, and vice versa. In one embodiment, the first carrier member 6 is provided with a number of radial guide slots 8. The second carrier member 7 is provided with a number of radially offset guide slots 9, as illustrated in FIG. 2. The radial guide slots 8 and the radially offset guide slots 9 are adapted to guide the tiltable axles 5. The axles 5 are adjustable to achieve a desired ratio of input speed to output speed during operation of the CVT. In some embodiments, adjustment of the axles 5 involves control of the position of the first and second carrier members to impart a tilting of the axles 5 and thereby adjusts the speed ratio of the variator. Other types of ball CVTs also exist, like the one produced by Milner, but are slightly different.

The working principle of such a CVP of FIG. 1 is shown on FIG. 3. The

CVP itself works with a traction fluid. The lubricant between the ball and the conical rings acts as a solid at high pressure, transferring the power from the input ring, through the balls, to the output ring. By tilting the balls' axes, the ratio is changed between input and output. When the axis is horizontal, the ratio is one, as illustrated in FIG. 3, when the axis is tilted, the distance between the axis and the contact point change, modifying the overall ratio. All the balls' axes are tilted at the same time with a mechanism included in the carrier and/or idler. 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 the 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 can 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, can 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 can 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 can 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 can be a

microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can 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 can 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 can be integral to the processor. The processor and the storage medium can 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 FIG. 4, in some embodiments, a vehicle control system 100 includes an input signal processing module 102, a transmission control module 104 and an output signal processing module 106. The input signal processing module 102 is configured to receive a number of electronic signals from sensors provided on the vehicle and/or transmission. The sensors optionally include temperature sensors, speed sensors, position sensors, among others. In some embodiments, the input signal processing module 102 optionally includes various sub-modules to perform routines such as signal acquisition, signal arbitration, or other known methods for signal processing. The output signal processing module 106 is optionally configured to

electronically communicate to a variety of actuators and sensors. In some embodiments, the output signal processing module 106 is configured to transmit commanded signals to actuators based on target values determined in the transmission control module 104. The transmission control module 104 optionally includes a variety of sub-modules or sub-routines for controlling continuously variable transmissions of the type discussed here. For example, the transmission control module 104 optionally includes a clutch control sub- module 08 that is programmed to execute control over clutches or similar devices within the transmission. In some embodiments, the clutch control sub- module implements state machine control for the coordination of engagement of clutches or similar devices. The transmission control module 104 optionally includes a CVP control sub-module 110 programmed to execute a variety of measurements and determine target operating conditions of the CVP, for example, of the ball-type continuously variable transmissions discussed here. It should be noted that the CVP control sub-module 110 optionally incorporates a number of sub-modules for performing measurements and control of the CVP. In some embodiments, the vehicle control system 100 includes an engine control module 112 configured to receive signals from the input signal processing module 102 and in communication with the output signal processing module 106. The engine control module 112 is configured to communicate with the transmission control module 104.

Referring now to FIG. 5, control and diagnostic methods described herein are related to continuously variable drives having a multiple speed gear box operably coupled to a continuously variable planetary device such as those described in reference to FIGS. 1-3, and disclosed in Patent Cooperation Treaty Patent Application no. PCT/US 17/026,041 , which is hereby incorporated by reference. As used herein, transmissions arranged in said way are generally referred to with the term "modular powerpath". As an illustrative example of a continuously variable drive, a schematic is depicted in FIG.5. It should be understood that there are a variety of architectures that the control and diagnostic methods described herein are applied to. In some embodiment, a continuously variable drive (CVD) 175 includes a continuously variable device 176 operably coupled to a multiple speed gear box or range box 177. In some embodiments, the continuously variable device 176 is controlled by the CVP control sub-module 110, and the multiple speed gear box 117 is controlled by the clutch control sub-module 108. It should be appreciated that the

transmission control module 104 is optionally adapted to control both the continuously variable device 176 and the multiple speed gear box 177. The CVD 175 includes a first rotatable shaft 178 adapted to couple to a source of rotational power (not shown). The continuously variable device 176 includes a variator 304 having a first traction ring assembly 305 and a second traction ring assembly 306. In some embodiments, the variator 304 is configured such as the variator depicted in FIGS. 1-3. The continuously variable device 176 includes a first planetary gear set 307 having a first ring gear 308, a first planet carrier 309, and a first sun gear 310. The first ring gear 308 is operably coupled to the first traction ring assembly 305. The first planet carrier 309 is operably coupled to the first rotatable shaft 178. The first sun gear 310 is operably coupled to the second traction ring assembly 306. In some

embodiments, the first sun gear 310 is operably coupled to a second rotatable shaft 179. The second rotatable shaft 179 is configured to couple to the multiple speed gear box 177. In some embodiments, the multiple speed gear box 177 is provided with a number of clutch devices including a forward mode clutch 180, a reverse mode clutch 181, a first-and-reverse mode clutch 182, a second-and-fourth mode clutch 183, and a third-and-fourth mode clutch 184. In some embodiments, the multiple speed gear box 177 includes a second planetary gear set 185. The second planetary gear set 185 has a second ring gear 186, a second planet carrier 187, and a second sun gear 188. In some embodiments, the second sun gear 188 is coupled to the third-and-fourth mode clutch 184 through a one-way clutch 194. The third-and-fourth mode clutch 184 is operably coupled to the forward mode clutch 80. The second ring gear 186 is coupled to the third-and-fourth mode clutch 184. In some embodiments, the multiple speed gear box 177 includes a third planetary gear set 189 having a third ring gear 190, a third planet carrier 191 , and a third sun gear 192. The third sun gear 192 is coupled to the second-and-fourth mode clutch 183 and the reverse clutch 181. The third planet carrier 191 is coupled to the second ring gear 186. The third ring gear 190 is coupled to the second planet carrier 187. The third ring gear 190 and the second planet carrier 187 are adapted to couple to an output drive shaft 193. The output drive shaft 193 is adapted to transmit an output power from the CVD 175 through the range box 177.

Referring now to FIG. 6, during operation of the CVD 175 multiple modes of operation are achieved through engagement of the various clutching devices to provide modes corresponding to overlapping ranges of speed and torque. Typically, the first mode of operation corresponds to a launch mode of a vehicle from a stop. The subsequent modes engaged correspond to higher speed ranges. Likewise, the reverse mode of operation corresponds to a reverse direction of a vehicle equipped with the CVD 175. The table depicted in FIG. 6, lists the modes of operation for the CVD 175 and indicates with an "x" the corresponding clutch engagement or clutch position. For mode 1 operation, the forward mode clutch 180 and the first-and-reverse mode clutch 182 are engaged. For mode 2 operation, the forward mode clutch 180 and the second- and-fourth mode clutch 183 are engaged. For mode 3 operation, the forward mode clutch 180 and the third-and-fourth mode clutch 184 are engaged. For mode 4 operation, the forward mode clutch 180, the second-and-fourth mode clutch 183, and the third-and-fourth mode clutch 184 are engaged. For reverse mode operation, the first-and-reverse mode clutch 182 and the reverse mode clutch 181 are engaged.

Turning now to FIG. 7, in one embodiment, the transmission control module 104 includes a speed ratio control process or method 400 that is used to control continuously variable drives such as the one described in reference to FIGS. 5 and 6. The speed ratio control process 400 receives a vehicle speed signal 401 from the input signal processing module 102. The vehicle speed signal 401 is indicative of a speed of a vehicle equipped with the continuously variable drive. The speed ratio control process 400 receives a driver's demand signal 408. In some embodiments, the driver's demand signal 408 originates from an accelerator pedal position signal or a throttle pedal position signal. The vehicle speed signal 401 is passed to a first look-up table 402. The first look-up table 402 contains values of a CVD reference ratio as a function of vehicle speed and driver demand. The first look-up table 402 returns a commanded CVD speed ratio 404. The speed ratio control process 400 receives a current CVD speed ratio signal 403 from the input signal processing module 102, for example. In some embodiments, the current CVD speed ratio signal 403 is a measured or actual speed ratio of the CVP. The current CVD speed ratio signal 403 is subtracted from the result provided by the first look-up table 402 to form a CVD speed ratio error 410. In some embodiments, the CVD speed ratio error 410 is passed to a diagnostic module implemented in the transmission controller 104. The CVD speed ratio error 410 is used to determine a CVD speed ratio PID Out 409. In some embodiments, a typical PID control feedback is implemented for the commanded CVD speed ratio 404. The CVD speed ratio PID Out 409 is passed to a second look-up table 405 to determine a reference CVP speed ratio. The second look-up table 405 contains values for the reference CVP speed ratio as a function of the CVD speed ratio PID Out 409. The speed ratio control process 400 receives a current CVP speed ratio signal 406 from the input signal processing module 102, for example. The current CVP speed ratio signal 406 is subtracted from the result of the second look-up table 405 to form a CVP speed ratio error 411. The CVP speed ratio error 411 is used to determine a commanded CVP speed ratio 407 that is used for diagnostic purposes in other modules of the transmission controller 104. During operation, the CVP speed ratio is in open loop control. During normal operation, the open loop CVP speed ratio reference, for example commanded CVP speed ratio 407, enables the closed loop CVD control of the speed ratio control process 400 to determine the health of the overall CVD.

In some embodiments, the speed ratio control process 400 includes a CVD speed ratio closed loop PID control, determining the CVD speed ratio PID Out 409 that is passed to an open loop CVP ratio command, for example, the second look-up table 405. Because the overall CVD ratio is the dominant goal and most apparent to the driver, this control structure has the advantage of compensating for variation in CVP performance by maintaining stable CVD operation independent of CVP state (excluding complete failure of CVP). In some embodiments, the control module enables the following diagnostic advantages including, but not limited to, fault isolation able to diagnose CVD faults and/or CVP faults, small CVP slip faults are compensated for by closed loop CVD ratio control, large slip faults unable to be compensated for are labeled gross CVP slip faults, input split planetary damage detected when CVP ratio control is tracking correctly but CVD ratio is not.

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 can 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.

Claims

WHAT IS CLAIMED IS:

1. A method for controlling a continuously variable drive (CVD) having a ball-planetary variator (CVP) provided with a ball in contact with a first traction ring assembly, a second traction ring assembly and an idler assembly, wherein the CVP is operably coupled to a multiple speed gear box, the method comprising the steps of:

receiving a plurality of input signals indicative of a vehicle speed, a current CVD speed ratio, and a current CVP speed ratio;

determining a commanded CVP speed ratio based at least in part on the current CVD speed ratio; and

issuing the commanded CVP speed ratio to impart a change in operating condition of the CVD.

2. The method of Claim 1 , wherein determining a commanded CVP speed ratio further comprises determining a commanded CVD speed ratio.

3. The method of Claim 2, wherein determining a commanded CVD speed ratio further comprises determining a CVD reference speed ratio based on the vehicle speed.

4. The method of Claim 3, wherein determining a commanded CVP speed ratio further comprises determining a CVP reference speed ratio based on the commanded CVD speed ratio.

5. The method of Claim 4, wherein determining the commanded CVP speed ratio further comprises subtracting the current CVP speed ratio from the CVP reference speed ratio.

6. The method of Claim 1 , wherein the commanded CVD speed ratio is formed in a closed loop control method.

7. The method of Claim 6, wherein the closed loop control method is a PID control method.

8. The method of Claim 6, wherein the commanded CVP speed ratio is formed in an open loop control method.