WO2017114544A1 - Procédé pour commander une transmission à variation continue - Google Patents

Procédé pour commander une transmission à variation continue Download PDF

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Publication number
WO2017114544A1
WO2017114544A1 PCT/EP2015/025118 EP2015025118W WO2017114544A1 WO 2017114544 A1 WO2017114544 A1 WO 2017114544A1 EP 2015025118 W EP2015025118 W EP 2015025118W WO 2017114544 A1 WO2017114544 A1 WO 2017114544A1
Authority
WO
WIPO (PCT)
Prior art keywords
transmission
tcf
pulley
speed ratio
efq
Prior art date
Application number
PCT/EP2015/025118
Other languages
English (en)
Inventor
Adrianus Antonius Jacobus Maria VAN TREIJEN
Guillaume Gerard Hubertus Rompen
Original Assignee
Robert Bosch Gmbh
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 Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Priority to PCT/EP2015/025118 priority Critical patent/WO2017114544A1/fr
Publication of WO2017114544A1 publication Critical patent/WO2017114544A1/fr

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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
    • F16H61/662—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 with endless flexible members
    • F16H61/66272—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 with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing
    • 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
    • F16H2061/0075—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 characterised by a particular control method
    • F16H2061/0087—Adaptive control, e.g. the control parameters adapted by learning
    • 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
    • F16H61/662—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 with endless flexible members
    • F16H61/66272—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 with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing
    • F16H2061/66277—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 with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing by optimising the clamping force exerted on the endless flexible member

Definitions

  • the present disclosure relates to a method for controlling, i.e. operating a belt- and-pulleys-type continuously variable transmission or CVT that is mostly used in the drive line of motorized vehicles for drivingly connecting the engine to the driven wheels while providing a continuously variable speed ratio there between. More specifically, the present, novel control method concerns the controlling of a normal force exerted in a friction contact between a drive belt and at least one pulley of such a transmission.
  • the term drive belt is generally descriptive and is intended to include, for example, both the well-known chain, pull belt and push belt types CVT drive belt.
  • a flexible drive belt is wrapped around and drivingly connects two variable pulleys.
  • a respective, essentially arc-shaped circumference section of the drive belt is located in between two conically shaped pulley discs of the respective pulley.
  • the pulley discs of each pulley are urged towards each other in axial direction by means of actuation means, such as a piston/cylinder-assembly, whereby a clamping force is exerted on the drive belt in axial direction at each pulley.
  • a component of such pulley clamping force is oriented perpendicular, i.e.
  • radial positions of the drive belt between the pulley discs of the transmission pulleys can be varied in mutually opposite radial directions, whereby the rotational speeds of the pulley can be continuously varied relatively to one another within a range of speed ratios provided by the transmission.
  • the relative radial positions of the drive belt at the pulleys are a/o determined by and can be controlled via the proportion between the said pulley clamping forces, in particular, a force component thereof, oriented perpendicular to the said normal force.
  • the transmission will assume a certain equilibrium speed ratio, which specific proportion, however, depends on other parameters as well, such as a torque (level) transmitted by and a rotational speed of the pulleys.
  • a minimally required pulley clamping force Fc_min (T ⁇ cos(1 ⁇ 2q>)) / (2 ⁇ R ⁇ TCF) (1 )
  • ⁇ is the angle defined between the conical pulley discs at the radial position R of the drive belt clamped between those pulley discs and TCF is a proportionality constant that is called the torque capacity factor and that is representative of the well-known coefficient of friction ⁇ .
  • the torque capacity factor TCF is defined and can be determined as follows:
  • TCF (T_max ⁇ cos(1 ⁇ 2q>)) / (2 ⁇ R ⁇ Fc) (1 b)
  • T_max is pulley torque that can be maximally be transmitted at a given level of the pulley clamping force Fc.
  • Equation (2) Sf is a safety factor between the said minimally required Fc-min and the actually applied pulley clamping force Fc.
  • the same clamping force Fc is applicable to both pulleys for transmitting the torque T, since the factor T/R in equation (1 ) is approximately constant, i.e. apart from friction losses.
  • the clamping force Fc can be applied at only one pulley, whereas the clamping force at the other pulley Fch needs to be set a higher level, as follows:
  • Fch Fc * EFQ(i) (3) if EFQ(i) ⁇ 1
  • Fch Fc / EFQ(i) (3b) if EFQ(i) ⁇ 1
  • EFQ(i) is the quotient of, i.e. the proportion between the two pulley clamping forces Fc and Fch that is required for transmission to maintain a specific and constant speed ratio i.
  • equilibrium force quotient EFQ(i) varies to a smaller or larger extend in relation to several operating parameters of the transmission.
  • the transmission efficiency could be improved by decreasing the uncertainty and/or variability of the torque capacity factor TCF that is relied upon to determine the pulley clamping forces Fc, Fch during operation of the transmission.
  • the (value of the) torque capacity factor TCF used by the transmission control system to determine the pulley clamping forces Fc and Fch is adapted during the service life of the transmission in relation to the (value of the) said equilibrium force quotient EFQ(i), in particular in relation to changes therein that occur during such service life.
  • a possible implementation of the control method according to claim 1 wherein the torque capacity factor TCF (used by the transmission control system to determine the pulley clamping forces Fc and Fch) is adapted during the service life of the transmission in relation to the (value of the) said equilibrium force quotient EFQ(i), is as follows. Firstly, the torque capacity factor TCF and the equilibrium force quotient EFQ(i) of one or more sample transmissions are determined both at the start of the service life and after the prolonged use thereof, e.g. at the end of (service) life. Secondly, by relating the thus observed change in the torque capacity factor ATCF during the transmission's service life to the thus observed change in the equilibrium force quotient AEFQ(i), a proportionality factor PF is calculated, as follows:
  • ATCF TCF_start - TCF_end (4)
  • AEFQ(i) EFQ(i)_start - EFQ(i)_end (5)
  • TCF_start is the torque capacity factor TCF at the start of transmission service life
  • TCF_end is the torque capacity factor TCF at the end of life
  • EFQ(i)_start is the equilibrium force quotient EFQ(i) at the start of transmission service life
  • EFQ(i)_end is the equilibrium force quotient EFQ(i) at the end of life.
  • the control system of the commercial, mass produced version of the transmission is programmed with such proportionality factor PF and to include it in determining the pulley clamping force Fc during operation. This might be implemented as follows:
  • TCF_est TCF_start - PF ⁇ (EFQ(i)_start - EFQ(i)_act) (7)
  • Fc (T ⁇ cos(1 ⁇ 2q>)) / (2 ⁇ R ⁇ TCF_est) ⁇ Sf (8)
  • TCF_est is the current estimate of the torque capacity factor TCF and EFQ(i)_act is the current, i.e. actual value of the equilibrium force quotient EFQ(i) at any given point in time during the transmission service life.
  • TCF_est C1 ⁇ EFQ(i)_act + C2 (9)
  • C1 and C2 are experimentally determined constants that quantify the said absolute correlation between the estimate of the actual torque capacity factor TCF_est and the actual equilibrium force quotient EFQ(i)_act.
  • control method according to claim 1 may be selectively applied in dependency on the instantaneous transmission operation conditions. For example, it may be applied in one or more specific speed ratios only, whereas in other speed ratios the conventional approach, using the worst case estimate of the torque capacity factor TCF, is applied.
  • the torque capacity factor TCF has been found to decrease gradually during the continued operation of the transmission, which is the ideal condition for applying the control method according to the present disclosure. Therefore, it is conceivable to apply the control method according to claim 1 in the said most accelerating speed ratio only.
  • a worst case estimate of the torque capacity factor TCF is applied according to the conventional transmission control approach.
  • it may be applied in steady state transmission conditions only, such as at a constant torque level or in a constant speed ratio, whereas in other, dynamic transmission conditions the conventional approach, using the worst case estimate of the torque capacity factor TCF, is applied.
  • Figure 1 provides a schematically depicted example of the well-known continuously variable transmission provided with two pulleys and a drive belt;
  • Figure 2 is a schematic illustration of the known electro-hydraulic control system of the known transmission
  • Figure 3 is a graph representing the measured value of a first operating parameter that is representative of the friction between the pulleys and the drive belt over a part of the service life of the transmission;
  • Figure 4 is a graph representing the measured value of a second operating parameter that is representative of a force balance between the pulleys over a part of the service life of the transmission; and in which: Figure 5 is a graph wherein the said first and second operating parameters of figure 3 and 4 are plotted against each other.
  • Figure 1 shows the central parts of a known continuously variable transmission or CVT that is commonly applied in the drive-line of motor vehicles between the engine and the driven wheels thereof.
  • the transmission comprises two pulleys 1 , 2 that are each provided with a pair of conical pulley discs 4, 5 mounted on a pulley shaft 6 or 7, between which pulley discs 4, 5 a predominantly V-shaped circumferential pulley groove is defined.
  • At least one pulley disc 4 of each pair of pulley discs 4, 5, i.e. of each pulley 1 , 2, is axially moveable along the pulley shaft 6, 7 of the respective pulley 1 , 2.
  • a drive belt 3 is wrapped around the pulleys 1 , 2, located in the pulley grooves thereof for transmitting a rotational movement and an accompanying torque between the pulley shafts 6, 7.
  • This type of transmission is commonly applied to provide a continuously variable speed ratio between an input or primary shaft 6 thereof that is connected to a prime mover, such as a vehicle engine E, and an output or secondary shaft 7 thereof that is connected to a load L, such as the driven wheels of a vehicle (see also figure 2).
  • the transmission also comprises of actuation means that -during operation- impose on the said axially moveable pulley disc 4 of each pulley 1 , 2 an axially oriented clamping force that is directed towards the respective other pulley disc 5 of that pulley 1 , 2, such that the drive belt 3 is clamped between these discs 4, 5 of the pulleys 1 , 2.
  • these pulley clamping forces not only determine a friction force between the drive belt 3 and the respective pulleys 1 , 2, but also a radial position R of the drive belt 3 at each pulley 1 , 2 between the pulley discs 4, 5 thereof, which radial position(s) R determine a speed ratio of the transmission between the pulley shafts 6, 7 thereof.
  • the actuation means are operated by an electro-hydraulic control system of the transmission that is illustrated in figure 2.
  • the known control system include an electronic transmission control unit or TCU that (directly or indirectly) determines the required pulley clamping force level for each pulley 1 , 2 based on a number of input variables V1 -Vx, such as engine throttle opening, engine rotational speed, etc., and that operates the actuation means so that the actually exerted pulley clamping forces coincide with such required levels.
  • TCU electronic transmission control unit
  • a primary clamping force Fp is generated by a primary pressure Ppri exerted in a pressure chamber 8 of a piston-and-cylinder assembly that is associated with the primary pulley 1 and a secondary clamping force Fs is generated by a secondary pressure Psec exerted in a pressure chamber 9 of a piston-and-cylinder assembly that is associated with the secondary pulley 2.
  • a hydraulic device of the electro-hydraulic control system comprises a hydraulic pump 10 for generating a flow fluid from a reservoir of hydraulic fluid at low pressure to a main hydraulic line 12 at high(-er) pressure.
  • the pressure of the hydraulic fluid in this main line 12, i.e. the pump or line pressure Pline, is controlled by means of a pressure control valve, i.e. a line pressure valve 13.
  • This line pressure valve 13 is provided with valve biasing means including a spring 13a, a valve actuator 13c and a pressure-feedback line 13b that together control the line pressure Pline.
  • the spring 13a ensures that a minimum pressure level is controlled, also in the absence of any controlled actuation of the line pressure valve 13 via the valve actuator 13c.
  • a force that is exerted by the spring 13a (acting on a valve body) is balanced by a force that is exerted by the line pressure Pline (acting on the valve body) via the pressure-feedback line 13b.
  • the line pressure valve 13 is arranged such that it is closed if the spring force is higher than the line pressure force and that it opens if the line pressure force exceeds the spring force. When it opens, the line pressure valve 13 allows fluid to pass from the main line 12 into an auxiliary line 14 of the hydraulic device.
  • the line pressure Pline can be controlled to a level above the said minimum pressure level determined by the spring 13a, by means of the valve actuator 13c that can exert a variable force (acting on a valve body as well). This actuator force is than additionally to be balanced by the line pressure Pline (acting on the valve body) via the pressure-feedback line 13b.
  • the valve actuator 13c allows the line pressure valve 13 to control the line pressure Pline between 5 and 75 bar.
  • the pressure of the hydraulic fluid in the auxiliary line 14, i.e. the auxiliary pressure Paux, is controlled by means of a further pressure control valve, i.e. an auxiliary pressure valve 15.
  • the auxiliary pressure valve 15 is provided with valve biasing means that consists (only) of a spring 15a and a pressure-feedback line 15b, which means that - in this example- the auxiliary pressure Paux is controlled to a predetermined pressure level.
  • the pressurized hydraulic fluid in the auxiliary line 14 is typically applied to operate one or more auxiliary hydraulic functions AF of the transmission such as the opening or closing of a clutch that may be provided in the drive line to (dis-)connect the load L from the engine E.
  • the auxiliary pressure valve 15 When it opens, the auxiliary pressure valve 15 allows fluid to pass from the auxiliary line 14 into a lubrication line 16 wherefrom moving parts of the transmission such as the drive belt 3 and shaft bearings are supplied with hydraulic fluid.
  • a further pressure control valve i.e. a lubrication pressure valve 17 is included to control a lubrication pressure Plub.
  • alternative arrangements of the electro-hydraulic control system i.e. the hydraulic device thereof, are known that do not rely on such lubrication pressure valve 17.
  • a primary pressure valve 20 is interposed between the main line 12 and a primary hydraulic branch 21 that hydraulically connects to the primary cylinder 8 and a secondary pressure valve 30 is interposed between the main line 12 and a secondary hydraulic branch 31 that hydraulically connects to the secondary cylinder 8.
  • Both the primary pressure valve 20 and the secondary pressure valve 30 are provided with valve biasing means of their own, respectively including a spring 20a; 30a, a valve actuator 20c; 30c and a pressure-feedback line 20b; 30b, which respective valve biasing means function similar to the valve biasing means of the line pressure valve 13 discussed hereinabove.
  • the primary valve 20 and the secondary valve 30 directly hydraulically connect the respective hydraulic branch 21 ; 31 and cylinder 8; 9 to the reservoir 1 1. This allows the primary pressure Ppri and the secondary pressure Psec to be reduced rapidly and to a low pressure level, determined solely by the force exerted by the spring 20a; 30a of the respective valve biasing means.
  • the TCU controls the pulley clamping force levels Fp, Fs indirectly controlling by the primary pressure Ppri and the secondary pressure Psec.
  • the TCU determines the levels of these pressures Ppri, Psec that are required to transmit the torque T from the primary pulley 1 to the secondary pulley 2 at a transmission speed ratio i, the TCU relies on a parameter called torque capacity factor TCF that is representative of the coefficient of friction between the drive belt 3 and the pulleys 1 , 2.
  • the torque capacity factor TCF is (relatively) high, so that the said clamping forces Fp, Fs and pulley pressures Ppri, Psec required for transmitting the said torque T can be (relatively) low.
  • a low estimate has to be used for the torque capacity factor TCF to, at least, account for a reduction thereof that occurs during the service life of the transmission due to the gradual wear of the drive belt 3 and the pulleys 1 , 2.
  • Figure 3 provides a typical example of the measured, actual value of the torque capacity factor TCF, i.e. TCF_act, in relation to the mileage travelled by the vehicle wherein the transmission is applied, which latter parameter is represented in the graph of figure 3 by the test duration t.
  • the solid line represents the measured torque capacity factor TCF_act for the most accelerating speed ratio of the transmission.
  • the commercially applied transmission typically lacks the functionality to directly measure the actual torque capacity factor TCF _act, at least such operating parameter cannot be measured with a sufficiently high accuracy.
  • the estimate of the torque capacity factor TCF_est is predetermined at a value below the (lowest) actual torque capacity factor TCF_act. From figure 3 it appears that this known approach results in a considerable over- dimensioning of the pulley pressures Ppri, Psec, at least in the initial stages of the test, i.e. at low vehicle mileage.
  • the actual torque capacity factor TCF_act represented in figure 3 cannot be easily determined during normal transmission operation, at least not with high accuracy.
  • the actual torque capacity factor TCF_act, or at least changes therein that occur during the continued operation, i.e. service life of the transmission can be approximated indirectly by relating these changes to a quotient EFQ(i) of the primary clamping force Fp and the secondary clamping force Fs in a constant speed ratio i, or to the changes therein.
  • This, so called, equilibrium force quotient EFQ(i) can be determined with high accuracy also during operation based on the pulley pressures Ppri, Psec.
  • Figure 4 provides a typical example of the measured, actual value of the equilibrium force quotient EFQ(i) in the most accelerating speed ratio and in relation to the test duration/test time t representing the mileage travelled by the vehicle wherein the transmission is applied. It may be observed that the solid line drawn through the measured equilibrium force quotient EFQ(i) values in figure 4 resembles the solid line drawn through the measured torque capacity factor TCF_act values in the most accelerating speed ratio in figure 3. These experimental data thus support the hypothesis underlying the present disclosure that the torque capacity factor TCF has an influence on the equilibrium force quotient EFQ(i).

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Transmission Device (AREA)

Abstract

L'invention concerne un procédé pour commander une transmission à variation continue comportant une courroie d'entraînement (3) et deux poulies (1, 2), comportant chacune deux disques de poulie (4, 5), entre lesquelles une force de serrage Fc, et, respectivement, Fch, peut être exercée sur la courroie d'entraînement (3) dans une direction axiale, dans lequel procédé des forces de serrage de poulie Fc, Fch sont déterminées pendant le fonctionnement par rapport à au moins un couple T devant être transmis par la transmission, à un rapport de transmission i produit par la transmission et à un paramètre TCF représentant le coefficient de frottement entre la courroie d'entraînement (3) et les poulies (1, 2). Selon l'invention, et pendant la durée de vie de la transmission, ledit paramètre TCF est conçu vis-à-vis d'un changement dans une proportion EFQ(i) entre les forces de serrage de poulie Fc, Fch qui sont requises pour maintenir un rapport de transmission constant i.
PCT/EP2015/025118 2015-12-29 2015-12-29 Procédé pour commander une transmission à variation continue WO2017114544A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2015/025118 WO2017114544A1 (fr) 2015-12-29 2015-12-29 Procédé pour commander une transmission à variation continue

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2015/025118 WO2017114544A1 (fr) 2015-12-29 2015-12-29 Procédé pour commander une transmission à variation continue

Publications (1)

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WO2017114544A1 true WO2017114544A1 (fr) 2017-07-06

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL1022242C2 (nl) 2002-12-23 2004-06-24 Doornes Transmissie Bv Werkwijze voor het bedienen van een continu variabele transmissie.
WO2005083304A1 (fr) 2003-12-01 2005-09-09 Robert Bosch Gmbh Transmission variable en continu
JP2007085396A (ja) * 2005-09-20 2007-04-05 Honda Motor Co Ltd ベルト式無段変速機の制御装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL1022242C2 (nl) 2002-12-23 2004-06-24 Doornes Transmissie Bv Werkwijze voor het bedienen van een continu variabele transmissie.
WO2005083304A1 (fr) 2003-12-01 2005-09-09 Robert Bosch Gmbh Transmission variable en continu
JP2007085396A (ja) * 2005-09-20 2007-04-05 Honda Motor Co Ltd ベルト式無段変速機の制御装置

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