EP1800026A1 - Continuously variable ratio transmission system - Google Patents

Continuously variable ratio transmission system

Info

Publication number
EP1800026A1
EP1800026A1 EP05784363A EP05784363A EP1800026A1 EP 1800026 A1 EP1800026 A1 EP 1800026A1 EP 05784363 A EP05784363 A EP 05784363A EP 05784363 A EP05784363 A EP 05784363A EP 1800026 A1 EP1800026 A1 EP 1800026A1
Authority
EP
European Patent Office
Prior art keywords
variator
gear
output
teeth
planet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05784363A
Other languages
German (de)
French (fr)
Inventor
Philip Duncan Winter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Torotrak Development Ltd
Original Assignee
Torotrak Development Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Torotrak Development Ltd filed Critical Torotrak Development Ltd
Publication of EP1800026A1 publication Critical patent/EP1800026A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H37/00Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00
    • F16H37/02Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings
    • F16H37/06Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts
    • F16H37/08Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with differential gearing
    • F16H37/0833Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with differential gearing with arrangements for dividing torque between two or more intermediate shafts, i.e. with two or more internal power paths
    • F16H37/084Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with differential gearing with arrangements for dividing torque between two or more intermediate shafts, i.e. with two or more internal power paths at least one power path being a continuously variable transmission, i.e. CVT
    • F16H37/086CVT using two coaxial friction members cooperating with at least one intermediate friction member
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H37/00Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00
    • F16H37/02Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings
    • F16H37/06Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts
    • F16H37/08Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with differential gearing
    • F16H37/0833Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with differential gearing with arrangements for dividing torque between two or more intermediate shafts, i.e. with two or more internal power paths
    • F16H37/084Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings with a plurality of driving or driven shafts; with arrangements for dividing torque between two or more intermediate shafts with differential gearing with arrangements for dividing torque between two or more intermediate shafts, i.e. with two or more internal power paths at least one power path being a continuously variable transmission, i.e. CVT
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16HGEARING
    • F16H61/00Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/66Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
    • F16H2061/6601Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with arrangements for dividing torque and shifting between different ranges

Definitions

  • a continuously variable ratio transmission unit (known as a variator) connected coaxially to the system input shaft and
  • train G is driven by a system input shaft I and carries a plurality of double-spur planetary gears P, one of the spurs X meshing with an input sun gear Z connected to the variator output shaft and the other of the spurs Y, identical in size to the first spur gear, meshing
  • the variator always transmits 100% of the input power from the engine and can operate over
  • Such transmission systems normally form part of a multi-regime transmission
  • the variator is designed to transmit 100% of the engine power, it must be built to withstand
  • a continuously variable ratio transmission system comprises:
  • a continuously variable ratio transmission unit (variator) connected coaxially to the system input shaft and having a coaxial variator output shaft; and a mixing planetary gear train having an input sun gear drivably connected to the
  • ratio Rl (the number of teeth on the input sun gear ⁇ by the number of
  • the power split is greatest at the variator ratio corresponding to synchronous ratio, where the demands on the variator are greatest.
  • the advantage is that the variator can be made more compact, as it never
  • Fig. 1 is a diagrammatic representation of a first embodiment of continuously
  • variable transmission in accordance with the present invention showing the principle of
  • Fig. 2 is a series of graphs showing the proportion of engine power transmitted by the variator with the arrangement of Fig. 1 for different values of R2/R1 (to be
  • Fig. 3 is a diagrammatic illustration of a second embodiment of continuously variable transmission in accordance with the present invention.
  • Fig. 4 is a digrammatic illustration of a known arrangement of continuously
  • toroidally-recessed discs 10 arranged one at each end of the unit and a pair of similar output discs 12, each facing a respective one of the input discs 10 and rotating with each
  • Sets of rollers 14 are mounted between the opposing faces of the input and output discs 10, 12 to transmit drive from the input discs 10 to the output discs 12 with a ratio which is variable by tilting the rollers 14.
  • roller is well known and will not be described further hereinafter.
  • the input discs 10 are connected to and driven by a system input shaft 16.
  • the variator provides an output via a tubular variator output shaft 18 which
  • the end of the shaft 18 remote from the variator V drives an input sun. gear S 1 of a planetary gear set Gl .
  • the sun gear Sl in turn drives a plurality of identical planetary gears Pl mounted on the carrier Cl .
  • the planet gears Pl are each mounted on the carrier Cl by
  • Rl is defined as [number of teeth on sun S 1 ⁇ by number of teeth on planet Pl]
  • gearing P is arranged so that R2 ⁇ Rl .
  • the sun gears Sl and S2 may both have 33 teeth
  • planetary gear Pl may have 23 teeth
  • planetary gear P2 may have 24 teeth.
  • Fig. 2 is a graph showing the proportion of engine power transmitted by the variator against the variator ratio, for different values of Rl/ R2 for a typical transmission.
  • the variator As the variator moves away from synchronous ratio, more of the engine power passes through the variator. Thus, the variator can be made more compact as it never transmits 100% of the engine power.
  • Fig. 1 The arrangement of Fig. 1 is a single-regime transmission to show the principle
  • Fig. 1 In practice, the arrangement of Fig. 1 would form the high-regime part of a multi-regime transmission. An example of such a transmission is illustrated in Fig.
  • gear input Rl typically of 25 teeth
  • output gear R2 typically of 27 teeth
  • annulus forms the carrier C2 for identical intermeshing radially inner and outer identical planetary gears P4 and P5 (typically having 16 teeth), the outer gear P4 of which meshes with a fixed annulus A2
  • gear set G2 The number of teeth for the components of the gear set G2 are given by way of example only.
  • planetary gears P2, P3 and planetary gears P4, P5 need not be identical.
  • V i.e. in a condition where the transmission output speed would be the same in both high

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)

Abstract

A continuously variable transmission comprises coaxial system input and output shafts (16, 20), a continuously variable ratio transmission unit (variator) (V) connected coaxially to the system input shaft (16) and having a coaxial variator output shaft (18) and a mixing planetary gear train (G1). The mixing planetary gear train has an input sun gear (S 1) drivably connected to the variator output shaft (18), a planet carrier (C 1) drivably connected to the system input shaft (16), a first planet gear (P 1) mounted on the planet carrier (C 1) and drivingly engaged with the input sun gear (S 1), a second planet gear (P2) mounted on the planet carrier (C 1) and arranged to rotate with the first planet gear (P 1) and drivingly engaged with an output sun gear (S2) connected to an output shaft (20). The ratio R1 (the number of teeth on the input sun gear ÷ by the number of teeth on the first planet gear) is set to be greater than R2 (the number of teeth on the output sun gear ÷ by the number of teeth on the second planet gear). This ensures that the variator always transmits less than 100% of the engine power, which allows the variator to be made more compact.

Description

DESCRIPTION
CONTINUOUSLY VARIABLE RATIO TRANSMISSION SYSTEM
It is known to provide a continuously variable ratio transmission system (CVT)
having coaxial system input and output shafts and a continuously variable ratio transmission unit (known as a variator) connected coaxially to the system input shaft and
having a coaxial variator output shaft. hi a typical arrangement, shown in Fig. 4, the carrier C of a mixing planetary gear
train G is driven by a system input shaft I and carries a plurality of double-spur planetary gears P, one of the spurs X meshing with an input sun gear Z connected to the variator output shaft and the other of the spurs Y, identical in size to the first spur gear, meshing
with an output sun gear W, identical to the input sun gear Z, which is connected to a
system output shaft O. The rotational speed of the system output shaft varies as the ratio
of the variator changes, and since the spurs X, Y of the planetary gears P are identical,
to each other and the input and output sun gears Z, W are identical to each other, the variator always transmits 100% of the input power from the engine and can operate over
its entire designed ratio spread.
Such transmission systems normally form part of a multi-regime transmission,
comprising a low regime which provides a system output ranging from reverse, thorugh a geared neutral to low forward speed and a high regime operating in the forward direction from low forward speed through to deep overdrive. Changing between the two
regimes is achieved by means of clutches to engage or disengage the appropriate gearing. Changing from one regime to the other is obtained at or very near so-called
"synchronous" ratio of the variator, i.e. a ratio which overlaps the high end of the low
regime and the low end of the high regime and at which the transmission output in either regime is the same (or very nearly so).
However, the variator is subjected to the highest stress at and around
synchronous ratio and is therefore designed always with this in mind. If, as is usual, the variator is designed to transmit 100% of the engine power, it must be built to withstand
the maximum available engine power, which therefore effectively limits the minimum size of the variator, having adverse effects on the size of the transmission as a whole.
It would therefore be desirable if the transmission could be arranged to reduce the proportion of power transmitted through the variator, particularly at and near
synchronous ratio where the demands on the variator are highest, as this would allow
more compact variators to be used. hi accordance with the present invention, a continuously variable ratio transmission system comprises:
coaxial system input and output shafts;
a continuously variable ratio transmission unit (variator) connected coaxially to the system input shaft and having a coaxial variator output shaft; and a mixing planetary gear train having an input sun gear drivably connected to the
variator output shaft, a planet carrier drivably connected to the system input shaft, a first
planet gear mounted on the planet carrier and drivingly engaged with the input sun gear, a second planet gear mounted on the planet carrier and arranged to rotate with the first
planet gear and drivingly engaged with an output sun gear connected to an output shaft;
wherein ratio Rl (the number of teeth on the input sun gear ÷ by the number of
teeth on the first planet gear) is greater than R2 (the number of teeth on the output sun gear ÷ by the number of teeth on the second planet gear).
IfRl = R2, the variator always transmits 100% of the engine power. By having
Rl > R2, a "power split" is created, whereby the variator always transmits less than 100%
of the engine power. The power split is greatest at the variator ratio corresponding to synchronous ratio, where the demands on the variator are greatest.
Although such an arrangement effectively reduces the ratio spread of the
transmission, the advantage is that the variator can be made more compact, as it never
transmits 100% of the engine power.
By way of example, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:-
Fig. 1 is a diagrammatic representation of a first embodiment of continuously
variable transmission in accordance with the present invention showing the principle of
the invention;
Fig. 2 is a series of graphs showing the proportion of engine power transmitted by the variator with the arrangement of Fig. 1 for different values of R2/R1 (to be
explained hereafter);
Fig. 3 is a diagrammatic illustration of a second embodiment of continuously variable transmission in accordance with the present invention; and
Fig. 4 is a digrammatic illustration of a known arrangement of continuously
variable transmission.
Referring firstly to Fig. 1, a continuously variable ratio transmission system
comprises a variator V of the known toroidal race rolling traction type having two
toroidally-recessed discs 10 arranged one at each end of the unit and a pair of similar output discs 12, each facing a respective one of the input discs 10 and rotating with each
other. Sets of rollers 14 are mounted between the opposing faces of the input and output discs 10, 12 to transmit drive from the input discs 10 to the output discs 12 with a ratio which is variable by tilting the rollers 14. The mechanism for, and control of, the tilt of
the roller is well known and will not be described further hereinafter.
The input discs 10 are connected to and driven by a system input shaft 16. One
end of the input shaft 16 is connected to the output of an engine and the opposite end of the input shaft 16 is formed into the carrier Cl of a planetary gear set which will be described in more detail hereafter.
The variator provides an output via a tubular variator output shaft 18 which
rotates with the output discs 12 and is arranged coaxially with the input shaft 16. The end of the shaft 18 remote from the variator V drives an input sun. gear S 1 of a planetary gear set Gl . The sun gear Sl in turn drives a plurality of identical planetary gears Pl mounted on the carrier Cl . The planet gears Pl are each mounted on the carrier Cl by
means of an associated shaft 19 which additionally carries an output planet gear P2 each of which meshes with, and drives, an output sun gear S2 which is connected to an output
shaft 20.
If Rl is defined as [number of teeth on sun S 1 ÷ by number of teeth on planet Pl]
and R2 as [number of teeth on sun S2 ÷ by number of teeth on planet P2], the planetary
gearing P is arranged so that R2 < Rl . For example, the sun gears Sl and S2 may both have 33 teeth, planetary gear Pl may have 23 teeth and planetary gear P2 may have 24 teeth.
By ensuring that R2 < Rl the power transmitted by the variator is always less than the power input from the engine. The effect of this can be seen from Fig. 2, which is a graph showing the proportion of engine power transmitted by the variator against the variator ratio, for different values of Rl/ R2 for a typical transmission.
Thus, it will be seen that as the engine approaches synchronous ratio, where the
load on the variator is highest, a relatively large proportion of the engine power bypasses
the variator. As the variator moves away from synchronous ratio, more of the engine power passes through the variator. Thus, the variator can be made more compact as it never transmits 100% of the engine power.
The arrangement of Fig. 1 is a single-regime transmission to show the principle
of the invention. In practice, the arrangement of Fig. 1 would form the high-regime part of a multi-regime transmission. An example of such a transmission is illustrated in Fig.
3, which shows the arrangement of the first embodiment as part of an embodiment of
two-regime transmission in accordance with the invention. The portion of the transmission illustrated and described for the first embodiment is used in high regime or
overdrive mode, in which the output shaft 20 is selectively connected to a reversing gear
set comprising gear input Rl (typically of 25 teeth) and output gear R2 (typically of 27 teeth) to a final output shaft 24 by applying a high regime clutch H between the output shaft 22 and the gear Rl .
In addition to the arrangement of the first embodiment, a gearing for low regime
comprises a second planetary gear set G2 and carrier Cl, on which are mounted a
plurality of planetary gears P3 meshing with, and identical to, planet gear P2 and with an annulus or ring gear Al (typically having 87 teeth). The annulus forms the carrier C2 for identical intermeshing radially inner and outer identical planetary gears P4 and P5 (typically having 16 teeth), the outer gear P4 of which meshes with a fixed annulus A2
(typically of 71 teeth) and the inner of which meshes with a further sun gear S3
(typically of 35 teeth) which is mounted on one end of a tubular output shaft 26 arranged
coaxially with output shaft 22. The number of teeth for the components of the gear set G2 are given by way of example only. In particular, planetary gears P2, P3 and planetary gears P4, P5 need not be identical.
Low regime operation is obtained by disengaging the high regime clutch H and connecting the tubular output shaft 26 to the reversing gear set by engagement of a low regime clutch L. Regime change takes place at or near synchronous ratio of the variator
V, i.e. in a condition where the transmission output speed would be the same in both high
and low regime. The invention is not restricted to the details of the foregoing embodiments.

Claims

1. A continuously variable transmission comprising:
coaxial system input and output shafts (16, 20);
a continuously variable ratio transmission unit (variator) (V) connected coaxially
to the system input shaft (16) and having a coaxial variator output shaft (18); and a mixing planetary gear train (Gl) having an input sun gear (Sl) drivably connected to the variator output shaft (18), a planet carrier (Cl) drivably connected to
the system input shaft (16), a first planet gear (Pl) mounted on the planet carrier (Cl)
and drivingly engaged with the input sun gear (Sl), a second planet gear (P2) mounted on the planet carrier (Cl) and arranged to rotate with the first planet gear and drivingly engaged with an output sun gear (S2) connected to an output shaft (20); wherein ratio Rl (the number of teeth on the input sun gear ÷ by the number of
teeth on the first planet gear) is greater than R2 (the number of teeth on the output sun
gear ÷ by the number of teeth on the second planet gear).
2. A continuously variable transmission as claimed in claim 1, comprising further gearing (G2) engaged with the second planet gear.
3. A continuously variable transmission as claimed in claim 2, further
comprising clutch means (H, L) for selectively engaging either the output shaft (20) or the output (26) of the further gearing (G2) as the transmission output.
EP05784363A 2004-09-20 2005-09-20 Continuously variable ratio transmission system Withdrawn EP1800026A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0420865A GB2418235A (en) 2004-09-20 2004-09-20 CVT with a compact variator which transmits less than 100% of engine power
PCT/GB2005/003622 WO2006032870A1 (en) 2004-09-20 2005-09-20 Continuously variable ratio transmission system

Publications (1)

Publication Number Publication Date
EP1800026A1 true EP1800026A1 (en) 2007-06-27

Family

ID=33306879

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05784363A Withdrawn EP1800026A1 (en) 2004-09-20 2005-09-20 Continuously variable ratio transmission system

Country Status (3)

Country Link
EP (1) EP1800026A1 (en)
GB (1) GB2418235A (en)
WO (1) WO2006032870A1 (en)

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GB0703351D0 (en) 2007-02-21 2007-03-28 Torotrak Dev Ltd Continuously variable transmission
US8578802B2 (en) 2009-12-16 2013-11-12 Allison Transmission, Inc. System and method for multiplexing gear engagement control and providing fault protection in a toroidal traction drive automatic transmission
CN105179672B (en) 2009-12-16 2017-07-11 艾里逊变速箱公司 The control loop of converter micro-tensioning system control method and converter
US8401752B2 (en) 2009-12-16 2013-03-19 Allison Transmission, Inc. Fail-to-neutral system and method for a toroidal traction drive automatic transmission
WO2011075243A1 (en) 2009-12-16 2011-06-23 Allison Transmission, Inc. Variator fault detection system
WO2011075427A1 (en) 2009-12-16 2011-06-23 Allison Transmission, Inc. System and method for controlling endload force of a variator
CA2784373C (en) 2009-12-16 2017-11-07 Allison Transmission, Inc. Fast valve actuation system for an automatic transmission
US8968152B2 (en) 2010-03-08 2015-03-03 Transmission Cvtcorp Inc. Transmission arrangement comprising a power mixing mechanism
EP2567123B1 (en) 2010-05-06 2016-03-23 Volvo Construction Equipment AB A continuously variable transmission and a working machine
KR20130131314A (en) 2010-08-16 2013-12-03 알리손 트랜스미션, 인크. Gear scheme for infinitely variable transmission
WO2012082845A2 (en) 2010-12-15 2012-06-21 Long Charles F Variator switching valve scheme for a torroidal traction drive transmission
US8721494B2 (en) 2010-12-15 2014-05-13 Allison Transmission, Inc. Variator multiplex valve scheme for a torroidal traction drive transmision
KR20140045302A (en) 2010-12-15 2014-04-16 알리손 트랜스미션, 인크. Dual pump regulator system for a motor vehicle transmission
DE112017001986T5 (en) * 2016-04-12 2018-12-20 Allison Transmission, Inc. Continuously variable transmission

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Also Published As

Publication number Publication date
GB0420865D0 (en) 2004-10-20
GB2418235A (en) 2006-03-22
WO2006032870A1 (en) 2006-03-30

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