WO2017067548A1

WO2017067548A1 - Method for ensuring a slip-free pressing process in a belt drive

Info

Publication number: WO2017067548A1
Application number: PCT/DE2016/200445
Authority: WO
Inventors: Michael Reuschel
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2015-10-22
Filing date: 2016-09-23
Publication date: 2017-04-27
Also published as: DE102016218335A1; DE112016004818A5

Abstract

The invention relates to a method for ensuring a slip-free pressing process in a belt drive in a motor vehicle. An input torque transmitted from a driveshaft of a drive unit to the belt drive is calculated electronically (only) on the basis of information of a drive unit controller, and a first pressing force of a driven disc set and a second pressing force of a driven disc set are set on the basis of the calculated input torque. The method has at least the following steps: a. ascertaining the calculated input torque for an existing operating point of the belt drive and determining the required first pressing force and second pressing force using a defined pressing rule or additionally using a pressing factor stored in an operation table; b. checking the first and the second pressing force by determining and analyzing the pressing force ratio using a zeta value of the first and the second pressing force and determining a correction value; and c. adapting the first and the second pressing force to a third and a fourth pressing force which have been correspondingly set on the drive belt while take into consideration the correction value.

Description

Method for ensuring non-slip contact pressure in a wrap-around transmission

The invention relates to a method for ensuring a non-slip contact pressure in a belt transmission in a motor vehicle.

Such a belt transmission is z. B. from WO 2006/063548 A1. For a permanently safe operation of such a belt transmission with a continuously variable transmission, a suitable contact pressure between the belt and the conical pulleys is decisive. Suitable means that the

Pressing on the one hand ensures that the belt does not slip, and on the other hand is not unnecessarily high in order not to generate undue component loads and to deteriorate the efficiency due to the high hydraulic pressure to be provided.

In this case, mechanical contact pressure, z. B. from DE 101 39 121 A1, in which a torque sensor is used. Next electronic Anpresssysteme are known, which controls the pressing of the conical disks via hydraulic valves based on a drive unit torque information.

In these contact pressure systems, the contact forces of the conical disks are adjusted exclusively controlled, an adaptation to individually present sets of discs and changing operating conditions does not occur. Therefore, in order to reliably prevent slippage of the belt even in unfavorable friction conditions, usually a too high contact pressure is set. However, this measure leads to higher consumption and correspondingly higher carbon dioxide emissions.

From WO 2006/063548 A1 a method for diagnosing the contact pressure safety is also known. It is described that at a certain operating point of the drive unit, or of the motor vehicle, or of the belt drive. bes (ie, for example, when driving at constant speed of the drive shaft and / or at a constant input torque) a compensated load step is performed. From the change in the ratio of the belt transmission present in this operating point Anpresssicherheitsfaktor is determined, in which case a change in the contact forces for further optimization (ie for lowering) of Anpresssicherheitsfaktors can be made.

On this basis, the present invention has the object, at least partially overcome the disadvantages known from the prior art and in particular to propose a method which makes it possible to set a suitable contact pressure at each operating point and for an individual belt transmission, d. H. Excessive contact pressure is avoided, but slippage of the belt is prevented.

The object is solved by the features of the independent claims. Advantageous developments are the subject of the dependent claims. The features listed individually in the claims can be combined in a technologically meaningful manner and can be supplemented by explanatory facts from the description and details of the figures, with further embodiments of the invention are shown.

The invention relates to a method for ensuring a non-slip contact pressure in a belt transmission in a motor vehicle, wherein a transmitted from a drive shaft of a drive unit to the belt transmission input torque (only) is calculated electronically based on information of a drive unit control unit and a first contact force of a driving pulley and a second pressing force of a driven pulley set is adjusted on the basis of this calculated input torque, wherein the method comprises at least the following steps:

a. Determining the calculated input torque for a given operating point of the belt transmission and determining the required first contact force and second contact force based on a defined Anpressgesetzes or additionally based on a stored in a operating table Anpressfaktors; b. Checking the first and second contact forces by determining and evaluating the contact force ratio based on a zeta value of the first and second contact forces and determining a correction value;

c. Adjusting the first and second contact force taking into account the

Correction value to a third and fourth contact force, which are adjusted according to the belt transmission.

In particular, step b. in a suitable driving state, preferably cyclically performed. In particular, step b. performed at times in which a suitable operating point of the drive unit, or of the belt drive, or a suitable driving state of the motor vehicle (ie, for example, when driving at constant speed of the drive shaft and / or constant input torque) is present.

In this step b. the method known from WO 2006/063548 A1 for determining a contact pressure safety factor is carried out. The method described therein is hereby fully incorporated by reference. In the context of the present invention, however, not only the currently applied contact pressure factor is determined, but based on the determined contact pressure factor, an operating table is written in which correspondingly calculated correction values are stored. This, in step b. certain correction values can then be used for each operating point of the belt drive in order to adapt a first contact pressure factor determined at this operating point in such a way that the driving forces on the pulley sets of the belt drive are adjusted to a suitable level. For adaptation of the contact forces, therefore, a diagnosis according to WO 2006/063548 A1 is not first carried out, but instead correction values determined at an earlier point in time are used. This makes it possible to adapt the drive forces to the respective operating conditions of the belt transmission (ie, for example, consideration of manufacturing tolerances, age, lubrication, wear of components, etc.).

In particular, the operating table is filled on the basis of empirical values on the basis of only one determined correction value. This is in step b. (after only one year liger implementation of step b.) A complete operating table before, from the suitable for all driving conditions correction values can be taken.

Preference is given in step b. in each case only an incremental adaptation of the correction values is carried out; so that the risk of under pressure in case of misadaptation can be significantly reduced

In the operating table, the correction values are stored in particular as a function of the parameters gear ratio (between driving pulley set and driven pulley set) and input torque.

In particular, in the case of a defined actuation of an accelerator pedal (accelerator pedal or corresponding device on the motor vehicle), a predetermined additional contact pressure force is applied to that in step c. added adjusted contact forces and it will be adjusted according to changed fifth and sixth contact forces on the belt transmission.

In particular, in step b. calculated correction values are only partially taken into account in the previously determined correction values. Proportional here means that the newly determined correction value z. B. only 20%, in particular to 30%, preferably between 10% and 40%, is taken over. That is, the newly determined correction value and the correction value used in step c) are determined as follows: correction value = 0.8 ^* correction value (old) + 0.2 ^* correction value (new). Such a procedure is particularly advantageous for incremental adjustment of the correction value. In particular, such a faultiness of the measurement results z. B. be reduced by noise.

In particular, from the operation of an accelerator pedal, an input torque desired by a driver is calculated, and in step a. of the method used.

In particular, so before a changing input torque is detected on the belt transmission or on the drive unit, already from the Movement of the accelerator pedal an imminent change in the input torque can be anticipated.

Furthermore, a motor vehicle is proposed, at least comprising a drive unit and a belt drive connected to the drive unit via a drive shaft, which can be operated by the method according to the invention.

The invention and the technical environment will be explained in more detail with reference to FIGS. The figures show particularly preferred embodiments, to which the invention is not limited. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. Like reference numerals designate like objects. Show it:

1 shows the construction of a belt drive arranged in a drive train of a motor vehicle;

Fig. 2: the method; and

Fig. 3: curves for explaining the known from WO 2006/063548 A1

Process.

1 shows the structure of a belt drive 1 arranged in a drive train of a motor vehicle 1. A driven by a drive unit 4 with interposition of a clutch and a change-speed gearbox drive shaft 3 is rigidly connected to a first conical disk 25 of a driving pulley set 9. A second conical disk 26 is arranged rotationally fixed and axially displaceable on the drive shaft 3. Between a rigidly connected to the drive shaft 3 support member and the second conical disk 26 pressure chambers are formed by the pressurization of the contact force 8, 19, 23 is variable, with the second conical disk 26 in the direction of the first conical disk 25 can be pressed. Similarly, a driven pulley set 1 1 a rigidly connected to an output shaft 27 third conical disk 28 and an axially movable fourth conical disk 29 which is urged by pressurizing associated pressure chambers in the direction of the third conical disk 28. Between the two Sets 9 and 1 1 runs a belt 30, for example, a link chain to. The contact force 8, 10, 19, 20, 23, 24 with which the belt 30 frictionally abuts the conical surfaces of the conical disks 25, 26, 38, 29 is controlled by means of hydraulic valves 31, 32, wherein the first hydraulic valve 31, for example, in itself Known manner determined by acting on the drive shaft 3 input torque 5 dependent Grundanpressung and with the second hydraulic valves 32, the translation adjustment. For controlling the hydraulic valves 31, 32 is an electronic control unit 14, at the inputs of which are signals from sensors which contain essential information for the control of the valves, which are correspondingly converted in the control unit 14 algorithms into control signals for the hydraulic valves.

In the method, with a defined actuation of an accelerator pedal 21 (accelerator pedal or corresponding device on the motor vehicle 2) by a driver 25, a predetermined additional pressure force 22 (determined, for example, in the control unit 14) is determined in step c. Adjusted contact forces 19, 20 added and it will be adjusted according to changed fifth and sixth contact forces 23, 24 on the belt transmission 1.

FIG. 2 shows the method whereby an input torque 5 transmitted from a drive shaft 3 of a drive unit 4 to the belt transmission 1 is calculated only electronically on the basis of information 6 of a drive unit control unit 7 and a first contact force 8 of a driving pulley 9 and a second contact force 10 of a driven pulley set 1 1 is set on the basis of this calculated input torque 5. In a step a. of the method, the calculated input torque 5 is determined for a present operating point 12 of the belt drive 1 and from a corresponding Anpressgesetz and a stored in an operating table Anpressfaktors in the context of step a. 13 the required first contact force 8 and second contact force 10 determined in one, in particular immediately then carried out step b. 16, a check or correction of the first and second contact force is performed by an appropriate adaptation, which z. B. by evaluating the Anpresskraftverhältnisses, ie the Zeta value, a statement to Anpressfaktors and thus to calculate the corresponding correction value 15 for this operating point 12). In a subsequent step c. 17 are the contact forces 8 and 10, taking into account the in step b. 16 adjusted to certain correction value 15. After this adaptation, the steps in step a. certain contact pressures 8, 10 are adjusted taking into account the correction value 15 to a third contact force 19 for the driving pulley 9 and a fourth contact pressure 20 for the driven pulley H and adjusted accordingly on the belt transmission 1 via the control unit 14 and the hydraulic valves 31, 32. By performing step b. 16, the correction values 15 of the operating table 15 are determined in a suitable driving state 18 of the motor vehicle 2.

In the method, with a defined actuation of an accelerator pedal 21 (accelerator pedal or corresponding device on the motor vehicle 2) by a driver 25, a predetermined additional contact force 22 (determined, for example, in the control unit 14) is determined in step b. 16 adapted contact forces 19, 20 added and it will be adjusted according to changed fifth and sixth contact forces 23, 24 on the belt transmission 1.

In FIG. 3, the abscissa indicates the inverse contact pressure factor SF 34 (1 / SF), which describes the ratio of the theoretically required contact force - which is required for suitable operation of the variator - to the existing contact force. A value of 1 means a contact pressure near the slip limit. For operation, a value for SF of approx. 1 .1 to 1 .3 sought. The ordinate indicates the value zeta. The curves A and B are two examples of a family of curves and represent the course of Zeta for two different and each constant gear ratios, wherein the curve B a longer translation than the curve A, ie a translation in the direction of overdrive (marked by arrow OD). Such Zeta curves provide similar form for any type of belt transmissions. The letters x, y, and z each point to different areas, x to an area to the left of the Zetamax point whose area is denoted by y, and z to an area to the right of the Zetamax point. The dashed lines indicated circular cutout is shown in Fig. 3 enlarged fully extended and illustrates the following process: starting from a stable state I on the zeta curve A with a given contact pressure, translation, input torque and zeta value is at constant or at least approximately constant Mo. - given a defined force jump on both disc sets. This is possible by appropriate control of the hydraulic valves 31, 32 of FIG. 2. The respective height of the force jump on the driving pulley set 9 and the driven pulley set 1 1 is determined in such a way that the value of zeta does not change, that is to say:

Zeta = (Fss1 / Fss2) = (Fss1-deltaFssl) / (Fss2-deltaFss2), where Fss1 is the first driving force 8 acting on the driving pulley set 9 before the force jump, Fss2 is the second driving force acting on the driven pulley set 1 1 before the force jump 10 is and deltaFssl the force jump

at the driving pulley set 9 and deltaFss2 is the force jump at the driven pulley set 1 1.

From the relation results for a "zeta-compensated" force jump: deltaFssl = Zeta ^* deltaFss2.

As shown in FIG. 3, such a zeta-compensated force jump causes the transmission state to move from state I to state II, i. the translation changes towards overdrive (OD) if the point I is to the left of Zetamax or moves in the direction of underdrive (UD) (marking by arrow UD), if the point I is sufficiently far to the right of Zetamax. A point III at the same contact pressure F and the same ratio as in point I is available only at a reduced zeta value, i. can not adjust. The translation adjustment (transition from the zeta curve A to the zeta curve B) can be diagnosed directly by the output signals from speed sensors 33 (see FIG. 1) connected to the controller 14 or by diagnosing the behavior of one in the controller 14 contained translation controller.

The method described with reference to FIG. 3 can be used, on the one hand, to diagnose the respective momentary contact pressure factor 34 by carrying out a compensated load step, as described with reference to FIG. 3, in suitable operating states of the vehicle while driving. It is understood that The load jump can also be carried out in the form of a Zeta-compensated reduction of the contact forces, with the conditions of FIG. 3 reversing in accordance with the direction. The contact security factor 34 is very high when a compensated load step results in a ratio change in the direction OD (the system is in the range x).

LIST OF REFERENCE NUMBERS

wrap-around

motor vehicle

drive shaft

drive unit

input torque

information

Drive unit controller

first contact force

driving pulley set

second contact force

driven pulley set

operating point

Step a. of the procedure

control unit

Correction value

Step b. of the procedure

Step c. of the procedure

driving condition

third contact force

fourth contact force

accelerator

Zusatzanpresskraft

fifth contact force

sixth contact force

first cone pulley

second cone pulley

output shaft

Third cone pulley

Fourth cone pulley

endless

First hydraulic valve Second hydraulic valve

Speed sensor

Anpresssicherheitsfaktor

Claims

claims

Method for ensuring slip-free contact pressure in a wrap-around transmission (1) in a motor vehicle (2), wherein an input torque (5) transmitted by a drive shaft (3) of a drive unit (4) to the belt transmission (1) is only electronically based on Information (6) of a drive unit control unit (7) is calculated and a pressing force (8) of a driving pulley set (9) and a pressing force (10) of a driven pulley set (1 1) on the basis of this calculated input torque (5) is set, the method at least the following steps include:

a. Determining the calculated input torque (5) for an existing operating point (12) of the belt drive (1) and determine the required first contact force (8) and second contact pressure (10) based on a defined Anpressgesetzes or additionally based on a stored in a operating table Anpressfaktors; b. Checking the first and second contact forces (8, 10) by determining and evaluating the contact force ratio based on a zeta value of the first and second contact forces (8, 10) and determining a correction value (15);

c. Adjusting the first (8) and second pressing force (10) taking into account the correction value (15) to a third contact force (19) and fourth contact force (20), which are adjusted according to the belt transmission.

The method of claim 1, wherein step b. is carried out in suitable operating states.

The method of claim 2, wherein in step b. determined correction values (15) are only partially taken into account in the previously determined correction values (15).

4. The method according to any one of the preceding claims, wherein the Anpressfaktor is dependent on the operating point.

5. The method according to any one of the preceding claims, wherein at a defined operation of an accelerator pedal (21) a predetermined additional contact pressure (22) on the in step c. adjusted contact pressure (19, 20) is added and adjusted accordingly fifth and sixth contact forces (23, 24) on the belt wrap (1) can be adjusted.

6. The method according to any one of the preceding claims, wherein from the operation of an accelerator pedal (21) by a driver (25) desired input torque (5) is calculated and in step a. of the method is used.

7. Motor vehicle (3), at least comprising a drive unit (4) and a thus via a drive shaft (3) connected Umschlingungsgetnebe (1), which is operable by the method according to the preceding claims.