CN115066566A

CN115066566A - Friction device and method for determining a characteristic variable of a pressure-controlled friction device

Info

Publication number: CN115066566A
Application number: CN202180013322.8A
Authority: CN
Inventors: 格奥尔·格珀特
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2020-03-12
Filing date: 2021-02-08
Publication date: 2022-09-16
Also published as: DE102021104069A1; WO2021180263A1

Abstract

The invention relates to a method (216) for determining a characteristic variable (106) of a friction device (12) arranged in a drive train (10) of a vehicle, said friction device having a first controllable friction element (12.1) and a second controllable friction element (12.2) arranged in parallel with the first friction element (12.1) and being provided with a drive element (14) that can be rotated at a drive rotational speed (na) for providing a drive torque (Ma) that generates a first and/or a second transmission torque (M1, M2), and a first characteristic variable (106) of the second friction element (12.2) being determined in a first operating state (204) of the vehicle. The invention further relates to a friction device (12) having a second friction element (12.2), the characteristic variable (106) of which can be determined by means of said method (216).

Description

Friction device and method for determining a characteristic variable of a pressure-controlled friction device

Technical Field

The invention relates to a method for determining a characteristic variable of a pressure-controlled friction device according to the preamble of claim 1. Furthermore, the invention relates to a friction device according to claim 10.

Background

A method for determining characteristic variables is known, for example, from DE 102014219325 a 1. A drive train with a drive motor is described, which is connected to a first input side of a first clutch and to a second input side of a second clutch. The second output side of the first clutch is connected to the first transmission, and the second output side of the second clutch is connected to the second transmission. The transmissions have different transmission ratios and are coupled to one another on the output side. The transmission characteristic curve, in particular the clutch characteristic curve, of the second clutch is determined as follows: the first clutch is controlled to a positive first opening degree and the second clutch is controlled to a preset second opening degree, whereafter the second opening degree is varied and the drive motor is controlled to provide a constant drive torque. The transmission characteristic of the second clutch is determined by the torque change of the first clutch during the second opening degree change.

Disclosure of Invention

The aim of the invention is to determine the characteristic variables of a pressure-controlled friction device more simply and more precisely. The half-joint pressure of the friction device should be periodically found during operation. The friction device should be able to operate more reliably and more accurately.

At least one of the objects is achieved by a method for determining a characteristic variable of a pressure-controlled friction device having the features according to claim 1. This enables the half-joint pressure to be determined easily and accurately. The half-joint pressure can be achieved independently of knowledge of the drive torque. The half-joint pressure can be found multiple times during operation of the vehicle, so that possible movements of the half-joint pressure can be detected.

The friction device can be designed as a multiple clutch, preferably as a dual clutch. The respective transmission torque can be a corresponding clutch torque. The friction device can be designed as a brake device. The respective transmission torque can be a corresponding braking torque. The first friction element can be a first clutch. The second friction element can be a second clutch. The first friction element can be a first brake. The second friction element can be a second brake.

The first torque introduction element can be a first clutch input. The second torque introduction element can be a second clutch input. The first torque introduction element can be a stationary support element, in particular at the housing, for supporting the first transmission torque. The second torque introduction element can be a fixed support element, in particular at the housing, for supporting the second transmission torque. The first and second torque introduction elements can be connected to one another in a rotationally fixed manner, in particular are formed in one piece.

A friction device is operatively disposed between the drive element and the transmission. The first and/or the second torque introduction element can be connected to the drive element, in particular in a rotationally fixed manner. A friction device is operably disposed between the transmission and the housing. The first and/or the second torque introduction element can be connected to the housing in a particularly rotationally fixed manner.

In particular, in a slip state, there is a rotational speed difference between the input rotational speed and the output rotational speed.

The friction device can be associated with a trolley bridge. The friction device can be arranged directly at the axle.

The transmission can be a two speed transmission. The first gear ratio can be greater than or less than the second gear ratio. The second gear ratio can be greater than one. The transmission can be a planetary transmission.

The first operating state can be a driving operation with the above-mentioned first transmission torque being transmitted via a first clutch operatively arranged between the drive element and the transmission.

The first transmission torque can be applied to the first friction element before the slip state is initiated.

The change in the second transmission torque can be equal to the change in the first transmission torque.

The first and second friction elements can be connected to each other in a rotationally fixed manner on the input side. The first and second friction elements can have the same input rotational speed. The input rotation speed and the driving rotation speed can be equal.

The operating pressure can be transmitted by the operating fluid. The steering fluid can be a hydraulic fluid.

In a preferred embodiment of the invention, the half-joint pressure is an actuating pressure, with which a second, predetermined transmission torque is transmitted. The second transmission torque can be smaller than the maximum transmission torque that can be transmitted via the second friction element.

In a particular embodiment of the invention, the drive element is an electric motor. The vehicle can be an electric vehicle.

In a preferred embodiment of the invention, the change in the transmission state of the first friction element is a change in the first transmission torque and/or a change in the rotational speed. The change in the first transmission torque can be detected as a change in the rotational speed of the first output rotational speed of the first friction element by the slip state of the first friction element occurring when the transmission state of the first friction element changes.

In a particular embodiment of the invention, a change in rotational speed is detected as a change in the driving rotational speed. This enables a simple measurement of the change in the rotational speed.

In a preferred embodiment of the invention, the first operating state is a steady-state driving state with a time profile of the first transmission torque, which is limited at most to a change of the first transmission torque by a torque value. This makes it possible to determine the first characteristic variable more easily and imperceptibly to the driver of the vehicle.

In a particular embodiment of the invention, the determination of the first characteristic variable is interrupted if the change in the first transmission torque exceeds the torque value. In this way, it is possible to preset interrupt conditions for the method, by which the accuracy of the determination can be maintained.

In a preferred embodiment of the invention, in the first operating state the second friction element is disengaged and the transmission of the second transmission torque is interrupted. The vehicle can be moved by a first transmission torque applied at the first friction element, in particular at the first clutch.

In a particular embodiment of the invention, in the second operating state the second friction element is at least partially closed and a second transmission torque is transmitted. The second transmission torque can be smaller than the first transmission torque.

In order to achieve at least one of the objects indicated above, a friction device for a drive train of a vehicle is furthermore proposed, which has a first and a second friction element, the characteristic variables of which can be determined in a first operating state of the vehicle by a method having at least one of the characteristics indicated above.

Further advantages and advantageous embodiments of the invention result from the description of the figures and the drawings.

Drawings

The present invention is described in detail below with reference to the accompanying drawings. Showing in detail:

fig. 1 shows a powertrain with a friction device according to a particular embodiment of the invention.

Fig. 2 shows a characteristic curve of a pressure-controlled clutch of a friction device according to another specific embodiment of the present invention.

Fig. 3 shows a graph of a friction device when applying the method according to a particular embodiment of the invention.

Figure 4 shows a flow chart of a method of another particular embodiment of the present invention.

Detailed Description

FIG. 1 illustrates a powertrain 10 having a friction device in accordance with a particular embodiment of the present invention. The powertrain 10 is provided in a vehicle. The friction device is designed as a multi-clutch, preferably as a dual clutch 12, and is connected on the input side to a drive element 14 for providing a drive torque. The drive element 14 is designed as an electric motor having a rotor which is rotatable about a rotational axis and which is connected on the input side to the dual clutch 12.

The dual clutch 12 has a first clutch 12.1 and a second clutch 12.2 arranged in parallel active therewith. The first clutch 12.1 is operatively arranged between the drive element 14 and a first transmission stage 16.1 of the transmission 16. The first clutch 12.1 has a first torque introduction element 17.1 on the clutch input side, which is designed as a first clutch input and is connected to the drive element 14.

The second clutch 12.2 is arranged between the drive element 14 and a second transmission stage 16.2 of the transmission 16. The second clutch 12.2 has a second torque introduction element 17.2, which is designed as a second clutch input and is connected to the drive element 14, on the clutch input side.

The first gear stage 16.1 has a first gear ratio and the second gear stage 16.2 has a second gear ratio which is different from the first transmission. In particular, the first gear ratio is smaller than the second gear ratio. The first transmission can thus correspond to a higher gear and the second transmission ratio can correspond to a lower gear.

A common output of the transmission 16 is connected to at least one wheel 18. For example, the vehicle can be driven via the second transmission ratio by means of the applied drive torque and the closed second clutch 12.2 and at higher speeds by shifting, i.e. by the second clutch 12.2 being open and the first clutch 12.1 being closed, via the first transmission ratio.

The selective actuation of the first clutch 12.1 and of the second clutch 12.2 takes place in a pressure-controlled manner via an actuating pressure, which is provided by an actuating device as required. The actuating pressure can be transmitted by an actuating fluid, for example a hydraulic fluid.

The first clutch 12.1 can transmit a first transmission torque by actuation via the actuation pressure and the second clutch 12.2 can transmit a second transmission torque by actuation via the actuation pressure. The transmittable first transmission torque is related to the actuating pressure acting on the first clutch 12.1. The second transmittable torque is related to the actuating pressure acting on the second clutch 12.2. The control of the respective clutch 12.1, 12.2 by changing the actuation pressure in order to set the respective transmission torque at the clutch 12.1, 12.2 requires, in the pre-controlled mode, precise knowledge of the transmission characteristic curve of the respective clutch 12.1, 12.2.

Fig. 2 shows a transmission characteristic curve 102 of a pressure-controlled clutch of a friction device according to another specific embodiment of the invention. The friction device can be a multiple clutch and the clutch can be a first or second clutch of the multiple clutch. The transmission characteristic curve 102 is decisive for the pre-controlled operation of the clutch and in pressure-controlled clutches a relationship between the transmittable transmission torque M and the actuating pressure p is given with respect to the selectable half-joint pressure.

The transmission characteristic curve 102 is set during operation of the vehicle by: in the case of a large transmission torque 104, the coefficient of friction is determined and the transmission characteristic curve 102 is stretched or compressed as a function of the coefficient of friction. The adjustment is carried out with the aim that the transmission characteristic curve 102 matches the actual state of the clutch as precisely as possible. However, the accuracy of the transfer characteristic 102 so adjusted is limited to the accuracy of the half-joint pressure 106. Since this is usually determined only once after the production of the clutch, the accuracy of the adjusted transmission characteristic curve 102 is related to the deviation between the determined half-joint pressure 106 and the actual half-joint pressure. The greater the degree to which the half-joint pressure changes during operation, the less accurate the transfer characteristic curve 102. The half-joint pressure 106 is in this case in particular the actuating pressure p at a transmission torque M of 10 Nm.

Thus, adjusting the half-joint pressure 106 during operation of the vehicle, for example, by shifting the half-joint pressure 106 determined hitherto to the adjusted half-joint pressure 108, results in a more precisely adjusted transmission characteristic curve 110. The adjustment of the half joint pressure 106 corresponds here to a horizontal displacement of the transfer characteristic curve 102.

Fig. 3 shows a graph of a friction device when applying the method according to a particular embodiment of the invention. In the normal operating state of the vehicle, the drive torque Ma varies as a function of the request for forward movement of the vehicle. Assuming that the vehicle is driven via a drive torque Ma, which is transmitted via the first clutch, a first transmission torque M1, which is applied in a pressure-controlled manner at the first clutch, is correlated with the drive torque Ma.

In this case, a first output speed n1 is present at the first clutch and a second output speed n2 is present at the second clutch on the output side. The first and second output rotational speeds n1, n2 differ from each other due to the first and second gear ratios. The second output speed n2 is greater than the first output speed n1 due to the higher second gear ratio. The input-side drive rotational speed na can be dependent on the operating state of the first clutch transmitting the drive torque and is different from the first output rotational speed n 1.

If the driving operation of the vehicle transitions from the standard operating state 202 of the vehicle into the first operating state 204, a method for determining a characteristic variable of the second clutch is initiated. The first operating state 204 is preferably a steady-state operating state in which, for example, a constant drive torque Ma is applied. First, the first clutch is operating in a maintained slip state 206.

The drive torque Ma is set to remain constant and the second clutch is switched from the first operating state to a different second operating state. At the beginning of the first operating state, the second clutch is disengaged, and in the second operating state, the second clutch is partially operated. In the second operating state, the second clutch transmits the second transmission torque M2 from the second gear step onwards to the drive element, which is subjected to the speed change 208 by the increased second output speed n2 of the second clutch. Furthermore, the second transmission torque M2 is additionally applied to the drive element on the input side and is automatically compensated for by the slip control of the first clutch, so that a change 210 in the first transmission torque M1 is caused, in this case in the form of an increase. The change in the transmission state of the first clutch is detected in a measurement 212 as a function of a change 210 in the first transmission torque M1 and a change 208 in the rotational speed at the first clutch, and the actuation pressure prevailing in the second actuation state of the second clutch is detected as the half-joint pressure. The half joint pressure is computationally linked to a reference value of the second transfer torque M2, which is detected via a change in the transmission device of the first clutch. The switched change 214 of the second transmission torque M2 corresponds to the change 210 of the first transmission torque M1. In this way, a change 210 of the first, large transmission torque M1 can be detected and converted into a corresponding change 214 of the second, small transmission torque M2. It is more accurate to detect the change when the transmission torque is large, so that the first characteristic variable can be detected more accurately.

A flow chart of a method 216 of another particular embodiment of the present invention is shown in fig. 4. At the beginning, there is a standard operating state 202 of the vehicle. The method is initiated when a first operating state 204 is present, in particular a steady-state operating state. The first clutch operates in a slip state 206 when the drive torque is constant.

Subsequently, the second clutch is switched from the first operating state to the second operating state and, when the steady-state second operating state is reached, a measurement 212 is initiated, wherein a change in the transmission state of the first clutch is detected and a first characteristic variable of the second clutch is ascertained as a function of said change.

If an astable delivery state 218 is determined during method 216, the method is interrupted. For example, the non-steady state transmission state 218 is present when the first transmission torque is greater than a predetermined torque value, for example when there is an acceleration request, in particular by actuating the accelerator pedal.

Description of the reference numerals

10 power assembly

12 double clutch

12.1 first Clutch

12.2 second Clutch

14 drive element

16 speed variator

16.1 first speed change stage

16.2 second speed change stage

17.1 first Torque introducing element

17.2 second Torque-introducing element

18 wheel

102 transfer characteristic curve

104 high transmission torque

106 half joint pressure

108 adjusted half-joint pressure

110 adjusted transfer characteristic curve

202 standard operating condition

204 first operating state

206 slip state

208 change of rotational speed

210 change

212 measurement

214 change

216 method

218 unstable transfer state

Ma drive torque

M1 first transfer torque

M2 second transfer torque

na drive rotational speed

n1 first output speed

n2 second output speed.

Claims

1. A method (216) for determining a characteristic variable (106) of a friction device (12) arranged in a drive train (10) of a vehicle, said friction device having: a first frictional element (12.1) which can be actuated for the releasable frictional transmission of a first transmission torque (M1) between the first torque introduction element (17.1) and a first transmission stage (16.1) of the transmission (16) having a first transmission ratio; and a second, operable friction element (12.2) which is arranged in parallel with the first friction element (12.1) and is operable to transmit a second transmission torque (M2) in a releasable frictional engagement between a second torque introduction element (17.2) and a second gear (16.2) of the transmission (16) having a second gear ratio which is different from the first gear ratio, and

a drive element (14) is provided which can be rotated at a drive rotational speed (na) for providing a drive torque (Ma) which causes the first and/or second transmission torque (M1, M2), and

in a first operating state (204) of the vehicle, a first characteristic variable (106) of the second friction element (12.2) is determined by: the first friction element (12.1) is operated in a slipping state (206), and during the slipping state (206) the drive torque (Ma) is set to remain constant, the second friction element (12.2) is switched from a first operating state into a second, different operating state, and a change (214) in the second transmission torque (M2) causes a change in the transmission state of the first friction element (12.1) by switching,

it is characterized in that the preparation method is characterized in that,

the actuating device provides an actuating pressure (p) for selectively actuating the first and second friction elements (12.1, 12.2) in a pressure-controlled manner, and

switching by changing the operating pressure (p), and

the first characteristic variable is a half-joint pressure (106) of the actuation pressure (p), which is determined as a function of a change in the transmission state of the first friction element (12.1).

2. The method (216) of claim 1,

characterized in that the half-joint pressure (106) is an actuating pressure (p), at which a second predetermined transmission torque (M2) is transmitted.

3. The method (216) of claim 1 or 2,

characterized in that the drive element (14) is an electric motor.

4. The method (216) of any of the above claims,

characterized in that the change in the transmission state of the first friction element (M1) is a change (210) in the first transmission torque (M1) and/or a change (208) in the rotational speed.

5. The method (216) of claim 4,

characterized in that the rotational speed variation (208) is detected as a variation of the driving rotational speed (Ma).

6. The method (216) of any of the preceding claims,

characterized in that the first operating state is a steady-state driving state having a time profile of the first transmission torque (M1) which is limited at most to a change in torque value of the first transmission torque (M1).

7. The method (216) of claim 6,

characterized in that the determination of the characteristic variable (106) is interrupted if the change in the first transmission torque (M1) exceeds the torque value.

8. The method (216) of any of the above claims,

characterized in that, in the first operating state, the second friction element (12.2) is disengaged and the transmission of the second transmission torque (M2) is interrupted.

9. The method (216) of any of the preceding claims,

characterized in that in the second operating state the second friction element (12.2) is at least partially closed and the second transmission torque (M2) is transmitted.

10. A friction device (12) for a drive train (10) of a vehicle,

comprising a first friction element (12.1) and a second friction element (12.2), wherein a characteristic variable (106) in a first operating state (204) of the vehicle can be determined by a method (216) according to one of the preceding claims.