DE19632747A1 - Method for pressure control of a CVT - Google Patents

Abstract

The invention pertains to a method for controlling pressure in a vari-speed transmission, based on a system with cone pulleys and belts, wherein a pressure calculation is made during partial braking. The reversal of the direction of rotation that occurs at the variable speed gear (4) upon partial braking is taken into account.

Description

The invention relates to a method for pressure control a CVT in overrun mode.

Continuously variable automatic transmission, hereinafter referred to as CVT usually consists of the following components: Starting unit, forward / reverse driving unit, variator, Intermediate shaft and differential. The variator in turn be consists of a pair of primary conical disks, a wrapping supply element and a pair of secondary conical pulleys. Every ke gel disc pair consists of a fixed in the axial direction standing conical disk and one in the axial direction sliding cone pulley. About the axial position of the Ke gel disks becomes the moment transfer ability and the Translation of the CVT determined. Such a structure is over ATZ Automobiltechnische Zeitschrift 96 (1994), No. 6, Page 380, known.

From Drive Technology 26 (1987), No. 8, page 45, is a General procedure for pressure calculation for a CVT knows. From EP-PS 0 451 887 the application is one of the like procedure in connection with two electronic Gearbox control units known.

In the prior art described above, none Differentiation between train and push operation made. There but in overrun the torque transmission direction on the Va riator inverted, the prior art has the disadvantage an incorrect pressure calculation.

The invention therefore has the task of boosting operation to ensure an error-free pressure calculation.  

The object is achieved by the Detection of overrun mode the pressure level in the adjustment room of the secondary disc pair is determined according to the formula:

p_SEK = (kP / kS) · cos α M_t · SF / (· 2µ · R · A_SEK)

here mean:

cos α: cosine of the cone pulley angle
M t: turbine torque
µ: Coefficient of friction of the conical pulley / belt element
R: Radius of the loop on the primary pulley
A_SEK: effective adjustment surface of the secondary disc
kP / kS: Force ratio primary / secondary disc
SF: safety factor.

The solution according to the invention has the advantage that the contact pressure calculation also takes into account that the primary disc in overrun to determine the torque the part of the variator.

In an embodiment of this, it is proposed that in overrun the turbine torque according to the following relation hung is calculated:

M_t = M_M + M_P + M_Sch + M_Vb + [J_Ges · (dω / dt)]

here mean:

M_M: torque given by the drive unit
M_P: Torque of the pump according to the contact pressure requirement
M_Sch: Drag torque of the drive unit
M_Vb: torque loss of the additional consumers
J_Ges · (dω / dt): Sum of the dynamic moments of all consumers that put pressure on the variator in overrun.

This configuration has the advantage that in the Calculation of the turbine torque on the one hand the dynamic Moment for the mass acceleration of all additional consumers and include a quasi-static part. The quasi The static part consists of the following parts together: current, from the drive unit in the drawer driven moment, absorption torque of the pump, Drag torque of the drive unit as a function of the tempera tur and the speed as well as loss torque of the additional consumption cher, such as B. steering aid, generator or air conditioning.

An embodiment is shown in the figures poses.

Show it:

1A shows a program flow chart ;

Fig. 1B is a pull / push characteristic and

Fig. 2 is a system diagram.

Fig. 1A shows a program flow chart for Druckbe calculation. The program begins with query S1 whether the vehicle is in overrun mode. The decision is made on the basis of a pull / push characteristic. This is shown in Fig. 1B. If it is determined in query S1 that the vehicle is in the train area, the pressure calculation for the variator takes place in step S3 according to the train calculation. If it is found in query S1 that the vehicle is in the pushing area, the pressure calculation is carried out in accordance with the pushing function in step S2. In step S4, the pressure value thus calculated for the variator is output in current values.

FIG. 1B shows a push / pull characteristic. Speed values of the drive unit, here motor speed n_Mot, are shown on the abscissa. Values of an accelerator pedal position or throttle valve information are shown on the ordinate. The actual pull / shear characteristic curve is shown with reference symbol A, values above the characteristic line A representing the pull range and values below the characteristic curve the shear range.

Fig. 2 is a highly schematic system diagram showing a CVT. With reference numeral 1 , an internal combustion engine is shown, consisting of the two blocks 5 for the moment of inertia, 6 for the torque given by the internal combustion engine in overrun mode and 7 for the intake moment of the pump. Reference numeral 2 denotes a hydrodynamic converter with its moment of inertia 8 . Reference 3 shows a forward drive clutch. Reference numeral 4 shows the variator, consisting of the primary conical pulley pair 11 , the secondary conical pulley pair 12 and the order loop 13th The primary pair of conical disks is adjusted via the force of the hydraulic medium on surface A1. The adjustment of the pair of secondary conical pulleys also takes place via the force effect of the hydraulic medium on surface A2.

As further blocks arranged in the drive train, reference numeral 9 shows the moment of inertia of the drive and reference numeral 10 the moment of inertia of the primary pulley set. The speed of the primary shaft 14 is measured via a speed sensor 16 . The speed of the secondary shaft 15 is measured via a speed sensor 17 ge. Reference numeral 18 shows a current / pressure converter, which converts current values into a pressure value for the forward drive clutch 3 . Reference numeral 19 shows a Druckmeßein direction for the pressure level of the secondary cone pulley pair. Reference numeral 20 designates an electronic transmission control unit which determines the required pressure level from the previously described input variables and additionally from the driving state detection train / push 21 .

For the overrun mode, the pressure level in the adjustment space of the secondary disc pair 12 is calculated according to the following formula:

p_SEK = (kP / kS) · cosα · M_t · SF / (2µ · R · A_SEK)

here mean:

cosα: cosine of the cone pulley angle
M_t: turbine torque
µ: Coefficient of friction of the conical pulley / belt element
R: Radius of the loop on the primary pulley
A_SEK: effective adjustment surface of the secondary disc
kP / kS: Force ratio primary / secondary disc
SF: safety factor.

The angle of the cone is under the cone pulley angle to understand the flank of the disc in relation to the horizontal e.g. B. 11 degrees. The power ratio kP / kS is usually se determined using a corresponding diagram. The sure one Safety factor is determined from tests.

The turbine torque is in turn according to the following Be draw calculated:

M_t = M_M + M_P + M_Sch + M_Vb + [J_Ges · (dω / dt)]

here mean:

M_M: torque given by the drive unit
M_P: Torque of the pump according to the contact pressure requirement
M_Sch: Drag torque of the drive unit
M_Vb: torque loss of the additional consumers
J_Ges · (dω / dt): Sum of the dynamic moments of all consumers that put pressure on the variator in overrun.

The turbine torque calculated in this way contains one dynamic factor J_Ges · (dω / dt) and a quasi-static Factor that is made up of the following variables: current elles moment M_M, Open given by the drive unit Torque of the pump M_P, drag torque of the drive unit depending on the temperature M_Sch and the speed and moment of loss of additional consumer M_Vb, such as Lenkhil fe, generator or air conditioning. The size drag  ment M_Sch of the drive unit is usually via a Map determined so that the following applies: M_Sch = f (Teta, n_Mot). Here Teta means the coolant temperature and n_Mot the Speed of the drive unit. The map is like this designed that when the operating temperature of the Drive unit the influence on the size M_Sch towards zero goes. The size M_Vb can be from a map or a digital, e.g. B. Air conditioning "on" or "off", informa tion of the consumer.

Reference list

1 internal combustion engine
2 hydrodynamic converter
3 forward drive clutch
4 variator
5 Mass moment of inertia of the internal combustion engine
6 Thrust torque of the internal combustion engine
7 Pump torque
8 Mass moment of inertia of hydrodynamic converter
9 Mass moment of inertia drive
10 Mass moment of inertia primary block
11 pair of primary conical pulleys
12 pairs of secondary conical pulleys
13 looping device
14 primary shaft
15 secondary shaft
16 Speed sensor primary shaft
17 Secondary shaft speed sensor
18 Forward drive clutch pressure control
19 Pressure measuring device pair of secondary conical pulleys
20 electronic transmission control
21 Input variable train / push

Claims (5)

1. Method for pressure control of an electro-hydraulically controlled CVT of the conical pulley wrap type, in which the torque transmission is determined via the pressure level in the adjustment space of the secondary pulley pair and a translation is determined via the pressure level in the adjustment space of the primary pulley pair, characterized in that with the detection of overrun the pressure level in the adjustment space of the secondary pulley pair is determined according to the formula: p_SEK = (kP / kS) · cos α · M_t · SF / (· 2µ · R · A_SEK) where: cos α: cosine of the cone pulley angle
M_t: turbine torque
µ: Coefficient of friction of the conical pulley / belt element
R: Radius of the loop on the primary pulley
A_SEK: effective adjustment surface of the secondary disc
kP / kS: Force ratio primary / secondary disc
SF: safety factor. 2. The method according to claim 1, characterized in that in overrun the Turbinenmo element (M_t) is calculated according to the following relationship: M_t = M_M + M_P + M_Sch + M_Vb + [J_Ges · (dω / dt)]
here mean: M_M: torque output by the drive unit
M_P: Torque of the pump according to the contact pressure requirement
M_Sch: Drag torque of the drive unit
M_Vb: torque loss of the additional consumers
J_Ges · (dω / dt): Sum of the dynamic moments of all consumers that put pressure on the variator in overrun. 3. The method according to claim 2 characterized indicates that the pump torque (M_P) over a Map is determined, with input variables of the map the speed of the drive unit (n_Mot) and the setpoint of the contact pressure (p_ASW), so that applies: M_P = f (n_Mot, p_ASW). 4. The method according to claim 2 characterized records that the drag torque of the drive unit (M_Sch) determined via a map, so that the following applies: M_Sch = f (Teta, n_Mot), the input variable Teta being the Coolant temperature of the drive unit and n_Mot the Speed of the drive unit corresponds. 5. The method according to claim 4, characterized records that when the operating temperature is reached the drive unit the influence of the sum (M_Sch) goes from the map towards zero.