Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H61/00—Control 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
  • F16H61/66—Control 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
  • F16H61/664—Friction gearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H37/00—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00
  • F16H37/02—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings
  • F16H37/06—Combinations 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
  • F16H37/08—Combinations 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
  • F16H37/0833—Combinations 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
  • F16H37/084—Combinations 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
  • F16H37/086—CVT using two coaxial friction members cooperating with at least one intermediate friction member
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H61/00—Control 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
  • F16H61/04—Smoothing ratio shift
  • F16H61/06—Smoothing ratio shift by controlling rate of change of fluid pressure
  • F16H61/061—Smoothing ratio shift by controlling rate of change of fluid pressure using electric control means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H15/00—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by friction between rotary members
  • F16H15/02—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by friction between rotary members without members having orbital motion
  • F16H15/04—Gearings providing a continuous range of gear ratios
  • F16H15/06—Gearings providing a continuous range of gear ratios in which a member A of uniform effective diameter mounted on a shaft may co-operate with different parts of a member B
  • F16H15/32—Gearings providing a continuous range of gear ratios in which a member A of uniform effective diameter mounted on a shaft may co-operate with different parts of a member B in which the member B has a curved friction surface formed as a surface of a body of revolution generated by a curve which is neither a circular arc centered on its axis of revolution nor a straight line
  • F16H15/36—Gearings providing a continuous range of gear ratios in which a member A of uniform effective diameter mounted on a shaft may co-operate with different parts of a member B in which the member B has a curved friction surface formed as a surface of a body of revolution generated by a curve which is neither a circular arc centered on its axis of revolution nor a straight line with concave friction surface, e.g. a hollow toroid surface
  • F16H15/38—Gearings providing a continuous range of gear ratios in which a member A of uniform effective diameter mounted on a shaft may co-operate with different parts of a member B in which the member B has a curved friction surface formed as a surface of a body of revolution generated by a curve which is neither a circular arc centered on its axis of revolution nor a straight line with concave friction surface, e.g. a hollow toroid surface with two members B having hollow toroid surfaces opposite to each other, the member or members A being adjustably mounted between the surfaces
  • F16H2015/383—Gearings providing a continuous range of gear ratios in which a member A of uniform effective diameter mounted on a shaft may co-operate with different parts of a member B in which the member B has a curved friction surface formed as a surface of a body of revolution generated by a curve which is neither a circular arc centered on its axis of revolution nor a straight line with concave friction surface, e.g. a hollow toroid surface with two members B having hollow toroid surfaces opposite to each other, the member or members A being adjustably mounted between the surfaces with two or more sets of toroid gearings arranged in parallel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H37/00—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00
  • F16H37/02—Combinations of mechanical gearings, not provided for in groups F16H1/00 - F16H35/00 comprising essentially only toothed or friction gearings
  • F16H37/06—Combinations 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
  • F16H37/08—Combinations 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
  • F16H37/0833—Combinations 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
  • F16H37/084—Combinations 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
  • F16H2037/088—Power-split transmissions with summing differentials, with the input of the CVT connected or connectable to the input shaft
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H61/00—Control 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
  • F16H61/04—Smoothing ratio shift
  • F16H61/06—Smoothing ratio shift by controlling rate of change of fluid pressure
  • F16H61/065—Smoothing ratio shift by controlling rate of change of fluid pressure using fluid control means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H61/00—Control 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
  • F16H61/04—Smoothing ratio shift
  • F16H61/06—Smoothing ratio shift by controlling rate of change of fluid pressure
  • F16H61/065—Smoothing ratio shift by controlling rate of change of fluid pressure using fluid control means
  • F16H61/068—Smoothing ratio shift by controlling rate of change of fluid pressure using fluid control means using an orifice control valve

Definitions

• the present invention relates to continuously-variable-ratio transmissions (CVTs) e.g. for use in an engine-driven vehicle, and to hydraulic control systems for such CVTs.
• CVTs continuously-variable-ratio transmissions
• Transmissions which use a variator of the toroidal-race rolling-traction type to give the continuously-variable-ratio performance and clutches to move the transmission between one or other of two operating regimes.
• Such clutches are designed with interleaving friction plates actuated by hydraulic pistons. To avoid excessive drag when disengaged, the plates are positively separated by 'push off springs inco ⁇ orated in the clutch.
• the drive from the variator to the transmission output shaft is via a mixing epicyclic gear set in which the planet carrier is driven by the input shaft, the variator output disc drives the sun, and the epicyclic annulus is connected with the transmission output shaft.
• the low regime clutch can disengage at the same time as (or after) the high regime clutch engages to effect a regime change with minimal slip, shock or wear.
• high regime operation the transmission output shaft is driven via a fixed ratio chain from the variator output disc and movement ofthe variator rollers back towards their highest speed ratio positions will enable the transmission to achieve increasingly higher forward speed ratios right up to deep overdrive.
• a synchronous change of regime can only occur at one specific transmission ratio since it is only at this point that the oncoming clutch has no relative motion across its elements and can be engaged without substantial risk of shift shock. This is true whether the change is from low regime to high regime as above discussed, or in the contrary sense.
• the clutches take a finite time to fill and engage, the fill process must be started correspondingly early if the CVT is to provide a smooth continuously varying transmission ratio.
• low pressure fluid is used as the transmission approaches synchronous ratio to 'soft-fill' the clutch to a pressure just capable of overcoming the 'push off springs and closing the friction plates.
• the finite oil flow required for this purpose is accessed from the lubrication flow at a point downstream ofthe system control valves to provide a high volume low pressure flow of fluid to the clutch-actuating pistons. Since the low pressure applied to the clutch is not sufficient to create significant clutch capacity, soft fill can be started at any convenient time provided only that the clutch is full as the transmission reaches synchronous ratio.
• the present invention provides a control system for a multi-regime continually-variable-transmission driven by a prime mover and providing an output drive, the control system comprising first and second regime change clutches and means for initiating engagement ofthe otherwise unengaged clutch during regime change, said control system further including : first control means, for controlling the clutch apply pressure of one or other of the clutches; and second control means, for controlling the variator rollers, characterised in that the first and second control means are operable independently of each other thereby to achieve active control ofthe regime change.
• the first and second regime change clutch comprise hydraulically actuated clutches employing absolute pressures in a control circuit and the variator control employs differential pressures within said circuit.
• each clutch includes an actively engaged phase obtained by connecting the clutch to a trailing pressure within the circuit and a fully engaged phase obtained by connecting the clutch to a leading pressure within the circuit.
• each clutch is operably connected to and, at least initially, controlled by the lower ofthe two pressures employed to control the variator.
• each clutch is operably connected to the higher of the two pressures employed to control the variator subsequent to it having been connected to the lower pressure employed therein.
• the control system further includes supply means for causing the supply of hydraulic fluid to each clutch to vary between the two pressures within the circuit control.
• the control system further includes sequencing means for causing operation and completion ofthe actively controlled phase prior to the commencement of
• control system further includes electronic control means for initiating clutch operation in advance of a range change.
• control system further includes monitoring means for monitoring at least one property associated with variator operation thereby to determine in advance of the variator reaching synchronous ratio that a change in ratio is necessary and for signalling the electronic control means accordingly.
• said monitoring means includes one or more monitors for monitoring one or more of: engine speed; variator ratio; time; transmission ratio; clutch fill time and shift rate or rate of change of one or other thereof.
• the present invention also provides a multi-regime continually variable- transmission inco ⁇ orating a control system as described above.
• the present invention also provides a method of operating a control system for a multi-regime continually-variable transmission having first and second regime change clutches, the method comprising the steps of: firstly, during regime change, initiating engagement of the otherwise unengaged clutch before the variator reaches synchronous ratio such that the engine load created by the transmission varies and thereby induces a change of regime; secondly, completing regime change by disengaging the clutch associated with the regime from which the transmission has been changed and completing engagement of the clutch under engagement.
• the clutches comprise hydraulically operated clutches and each clutch comprises an actively engaged phase and a fully engaged phase and in which during the active phase the clutch is operably connected to a trailing pressure in a control circuit and during the fully engaged phase the clutch is operably connected to a leading pressure in the control circuit, and the method includes the further step of initiating clutch engagement by firstly connecting the clutch to the trailing pressure and completing engagement by connecting it to the leading pressure.
• the variator includes ratio varying rollers each associated with a respective hydraulic ram the method including the further step of supplying hydraulic fluid to the hydraulic ram such that the rollers respond to the differential pressure.
• the method includes the further step of monitoring one or more, parameters associated with the control system, transmission, or items associated therewith, thereby to determine when to commence said first and second steps.
• a hydraulic control system for a multi-regime continually variable transmission driven by a prime mover and providing an output drive, the transmission having hydraulically actuated first and second regime change clutches and a variator having ratio varying rollers each associated with a respective hydraulic ram, the system having, at any particular moment in time, a higher and a lower source of hydraulic pressure, supply means for causing the supply of hydraulic fluid to each clutch to vary between the fluid at the higher pressure and the fluid at the lower pressure and the supply of hydraulic fluid to the hydraulic ram to be such that the rollers respond to the differential pressure.
• Figure 1 shows a schematic circuit diagram for a hydraulic control system in accordance with the present invention
• Figure 2 shows, in outline form only, the CVT to be controlled by the system of Figure 1 ;
• FIG. 3 is a schematic representation of a drive system inco ⁇ orating aspects ofthe present invention.
• Figure 4 is a simplified version ofthe control system illustrated in the bottom half of figure 1.
• the CVT 8 shown there includes a variator 10 of the toroidal-race rolling-traction type comprising two input discs 12,13 (the latter splined to the variator shaft 15 for limited axial movement along the shaft), a central output disc 17, and two arrays of piston-controlled rollers engaging with the input and output discs to transmit torque between the discs in response to the torque demand on the variator.
• a variator 10 of the toroidal-race rolling-traction type comprising two input discs 12,13 (the latter splined to the variator shaft 15 for limited axial movement along the shaft), a central output disc 17, and two arrays of piston-controlled rollers engaging with the input and output discs to transmit torque between the discs in response to the torque demand on the variator.
• master roller 19 is shown in Figure 2.
• roller pistons be aligned so that they are substantially tangential to the centre circle of the imaginary toruses 21 of which the rotor races form part, but with a small inclination known as the W 97/40
• the variator input shaft 15 is powered at one end 23 from the engine (not shown) ofthe host vehicle while an axial load is imposed on the input disc at the other end of the variator by a pressure chamber 25 filled with high pressure hydraulic fluid from the same line 27.
• the pressure in line 27 is equal to the greater of the two pressures in lines 67, 68. the higher of which is employed as the control pressure or leading pressure fluid for roller piston 24.
• the trailing pressure fluid for piston 29 is provided from whichever of lines 67, 68 has the lower pressure. It will therefore be noted that the roller responds to the differential pressure across its control piston rather than to the absolute pressure values in lines 67 and 68.
• the transmission output shaft 33 is powered from the variator input shaft via gearing 35, a low regime clutch 37 and an epicyclic gear set 39 in known fashion.
• shaft 33 is additionally powered from the variator output disc 17 via a drive chain 41 and a high regime clutch 43.
• Reference numeral 45 indicates the output end of shaft 33, e.g. for connection with the host vehicle's differential and road wheels.
• the master roller 19 and the five "slave” rollers 47-51 and their associated control pistons and cylinders appear again in Figure 1 as do the two regime clutches 37 and 43, both of which are fitted with push-off springs rated to withstand a plate-closing pressure of up to 3 bar.
• the axle 52 ofthe master roller 19 is mounted in the cavity 53 ofthe hollow shaft 54 of a double-acting piston 55.
• This piston is formed with opposed piston heads 56, 57 which are both free to slide under hydraulic load within coaxial cylindrical caps 58, 59 and to rotate about the longitudinal axis of the shaft 54.
• piston 55 and end caps 58, 59 act to define a hydraulic ram 71 associated with each roller. It will be appreciated that this figure is purely schematic.
• item 55 is replaced by a single-headed design of double-acting piston e.g. as disclosed, for example, in GB 2227287 and depicted, for convenience only, in the diagrammatic representation of Figure 2.
• the hydraulic fluid inlets 61 , 62 and outlets 64, 65 for the master piston are formed in the end and side walls ofthe associated cylinder caps 58, 59 and pressure lines 67, 68 ensure that the various slave pistons behave in exactly the same way as master piston 29 so that all six variator rollers are continuously maintained at the same pressure as one another.
• the hydraulic control system 70 this comprises two independent oil pumps 72, 73 delivering hydraulic fluid from a sump 75 to the lines 67, 68 referred to above.
• a cross-connection 77 between these two lines communicates by way of a 'higher- pressure-wins' arrangement of non-return valves 79 and 80 with the flow line 27 in Figure 2.
• the outlets 64, 65 for the master piston end caps 58, 59 feed left-hand and right-hand pressure lines 82, 83. These are interconnected by a cross-connection 85 which communicates by way of a 'higher-pressure- wins' arrangement 87, 88 with a fully engaged circuit 90 for clutches 37, 43.
• a second cross-connection 92 communicates by a 'lower-pressure -wins' arrangement 94, 95 with the an actively engaged circuit 97 for the two clutches.
• Reference numerals 99, 100 indicate two electro-hydraulic pressure control valves which, in combination, effectively constitute first and second control means for controlling the clutch apply pressure and the variator rollers in a manner discussed in detail later herein.
• the pressure lines 82, 83 combine at 102 from whence a connection 104 provides low-pressure fluid for general lubrication of the transmission.
• each contains two electrically-operated solenoid valves 106, 107 and 109, 110 which can be switched to connect each of the clutches 37, 43 for "active-fill” or for " a fully engaged-fill” as required. From the situation illustrated in Figure 1, for example, switching the valve 106 will connect the low regime clutch 37 to the actively engaged circuit 97 whereas switching the valve 107 instead, will connect the low regime clutch 37 to the fully engaged circuit 90. Valves 109 and 110 operate in analogous fashion to valves 106 and 107 but in respect of the high regime clutch 43. The system is completed by two 1 bar restrictor plates 1 12, 1 13 located in lines 82,
• valve 99 in a typical case the pressure control valve 99 initially is receiving zero current and the valve 100 is receiving a ' ⁇ amp current. This means that the line pressure immediately upstream of valve 99 will be at roughly back-pressure (2 bar) and the next step is to switch valve 109 to fill the line between the valve 109 and clutch 43 with low pressure oil.
• valves 99. 100 are raised to 0.1 amps and 0.6 amps respectively to increase the adjacent line pressures typically from 2 bar to 3.6 bar (line 82) and from 10 bar to 11.6 bar (line 83).
• the pressure in line 82 is now sufficient to fill the high-regime clutch 43 at a rate determined by the control current for valves 99, 100.
• the control electronics shown schematically at 220 in fig 3, will assume that this phase has been completed and the system is held in readiness for the next phase.
• the first necessary step is that the valve currents are both raised to a same value, typically 2 amps, so as temporarily to 'cut out' the variator 10 from the transmission before switching valves 106, 107 to the positions illustrated in Figure 1 to disengage clutch 37.
• the current in valve 100 Prior to the subsequent release of clutch 37, the current in valve 100 is reduced to zero amps ( 2 bar) while that in valve 99 is reduced to l A amp ( 10 bar) so as to preset the pressure differential across the variator to that required for operation in the next regime. Further regime changes at either clutch will be carried out in an analogous fashion to those described above.
• FIG. 3 is a schematic representation ofthe present invention when combined with a conventional powertrain layout.
• control 220 comprises means 230 for monitoring any one or more of a number of properties associated with variator operation thereby to determine in advance of the variator reaching synchronous ratio that a change in ratio is necessary and for signalling the electronic control means 220 accordingly.
• Suitable monitors or measuring devices are well known in the art and are, therefore, not described herein. Parameters such as engine speed; variator ratio; time; transmission ratio; clutch fill time; shift rate; throttle pedal position; hydraulic pressure or rate of change of one or other thereof are all suitable candidates for monitoring.
• lines 242, 244 and 246 each represent links between suitable monitors 252, 254 and 256 positioned for monitoring the engine speed, variator output speed and epicyclic output speed and for supplying information relating thereto to control 220. Additionally, figure 3 shows a pedal position monitor of 248 and similarly connected to control 220.
• FIG 4 illustrates a slightly simplified version ofthe control shown in figure 2, it will be appreciated that various arrangements are possible.
• lines 82, 83 are connected to the clutch control circuit 300 at points A and B respectively.
• Control valves 99, 100 are connected to lines 82, 83 in the same manner as described with reference to figure 1.
• the valves continue to supply fluid to the lubrication circuit 104 and vary the pressures in the roller control rams 71.
• the control system 300 comprise four solenoid actuated valves 310, 312, 314 and 316.
• the first two valves are operable to take hydraulic fluid from one or other of A or B and pass that fluid onto associated secondary valves 314, 316 respectively.
• valves 99. 100 for varying the position thereof and hence varying P a and P b . Consequently, the control electronics can easily determine which is the greater ofthe two pressures within the circuit and cause the system to be operated accordingly. For example, whilst operating in drive forwards, the high pressure line is determined by the regime i.e. Low Regime could require the left line. High Regime the right. In over run and reverse drive the pressures reverse. Since the controller causes changes in the pressures within lines 82, 83 it can also change the clutch valve to connect the clutch to the correct line. Operation of the figure 4 arrangement from the low regime to the high regime follows the following sequence of events:
• valve 312 is in position 1 (line B) as is valve 316, thereby to supply high pressure fluid to maintain operation of low range clutch 37.
• valve 314 is in position 2 thus preventing the supply of any hydraulic fluid to the clutch and allowing any fluid in there from previous operation to drain via outlet 320 to sump 104.
• valves 310 and 314 In order to move from low range to high range it is necessary to initiate operation of valves 310 and 314 such as to direct low pressure fluid from A to the clutch. This is simply achieved by switching valve 310 to position 2 and valve 314 to position 1.
• the pressure at B (P B ) is greater than that at A (P A ) and. hence, the high clutch is said to be in the initial stage of active control phase.
• the low pressure fluid acts to close the clutch but provides insufficient presure to give the clutch capacity i.e. clamp the clutch plates and allow transmission of torque. Completion of this part of the phase can be determined by monitoring the time elapsed since commencement or monitoring other parameters in the system such as clutch position.
• valves 99. 100 are operated together to raise the pressures in both lines 82, 83 by equal amounts until P ⁇ is sufficient to cause a drag torque capable of moving the variator to synchronous ratio.
• the final step in this phase involves controlling P a and P b -P a such that the system moves to synchronism and the engaging clutch stops slipping. This is simply achieved by altering the current supplied to valves 99. 100 in the manner described above such that the engaging clutch causes a variation in engine speed such that it matches that required for synchronous operation. In effect, the engine load created by the transmission varies inducing the shift. Once the clutch has stopped slipping, the transmission is at synchronous ratio. If the engine is still producing torque, as is probable, the clutches must be maintained with enough pressure applied for their combined capacity to match the engine drive torque.
• valves 99, 100 constitute the first control means when operated together to simply raise or lower the pressure of the hydraulic fluid for end load pu ⁇ oses without altering the differential pressure used for roller control.
• These valves constitute the second control means when operated to vary the differential pressure experienced by the roller control pistons 55.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Control Of Transmission Device (AREA)
• Friction Gearing (AREA)
• Transmission Devices (AREA)

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Citations (4)

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• 1996
  • 1996-04-19 GB GB9608147A patent/GB2312258A/en not_active Withdrawn
• 1997
  • 1997-04-04 JP JP9537807A patent/JP2000509130A/ja not_active Ceased
  • 1997-04-04 BR BR9708773A patent/BR9708773A/pt not_active IP Right Cessation
  • 1997-04-04 WO PCT/GB1997/000956 patent/WO1997040296A1/en not_active Ceased
  • 1997-04-04 PL PL97329377A patent/PL186935B1/pl not_active IP Right Cessation
  • 1997-04-04 DE DE69716416T patent/DE69716416T2/de not_active Expired - Fee Related
  • 1997-04-04 EP EP97915604A patent/EP0894211B1/en not_active Expired - Lifetime
  • 1997-04-04 CA CA002251789A patent/CA2251789C/en not_active Expired - Fee Related
  • 1997-04-04 HU HU9901965A patent/HUP9901965A3/hu unknown
  • 1997-04-04 RU RU98120705/28A patent/RU2178109C2/ru not_active IP Right Cessation
  • 1997-04-04 AU AU23022/97A patent/AU723256B2/en not_active Ceased
  • 1997-04-04 CN CN97195356A patent/CN1113175C/zh not_active Expired - Fee Related
  • 1997-04-15 MY MYPI97001642A patent/MY118680A/en unknown

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