DE102012219697A1 - Drive unit for hybrid vehicle, has internal combustion engine, electric machine and transmission, where a transmission-internal multiple disk clutch is switched between shaft of internal combustion engine and shaft of transmission - Google Patents

Abstract

The drive unit (1) has an internal combustion engine (2), an electric machine (3) and a transmission (4), where a transmission-internal or transmission-external multiple disk clutch (6) is switched between a shaft of the internal combustion engine and a shaft of the transmission. The multiple disk clutch is gradually closed to start of the internal combustion engine during the transition from a purely electric drive of the hybrid vehicle in the hybrid drive of the hybrid vehicle such that the internal combustion engine transfers a torque from a portion of an inner plate to an outer plate. An independent claim is included for a method for operating a drive unit.

Description

The invention relates to a drive unit for a hybrid vehicle and a method for operating the same.

From the EP 2 311 680 A2 For example, a drive unit for a hybrid vehicle with an internal combustion engine, an electric machine and a transmission is known. Between a shaft of the internal combustion engine and a shaft of the transmission, a multi-plate clutch is connected, which is opened when the internal combustion engine is stationary during a purely electric drive and which is closed during hybrid driving with the internal combustion engine running. The multi-plate clutch has a plurality of recorded on an inner disc carrier inner plates and a plurality of recorded on an outer disc outer plates, the inner plates and the outer plates via a pressurized actuator, which is preferably designed as an actuating piston, against the restoring force of a preferably designed as a return spring return element for closing the multi-plate clutch are compressible.

During the transition from purely electric driving to hybrid driving in such a hybrid vehicle, the internal combustion engine must be restarted during the purely electric drive. This is preferably done via a so-called drag start, in which case the switched between the transmission and the engine multi-plate clutch, which is open when electrically driven, is closed.

This multi-plate clutch is designed for the transmission of high torques, whereby the problem is that by closing the multi-plate clutch, the starting of the internal combustion engine at the output is felt. This is perceived by the driver or passenger side as uncomfortable.

There is therefore a need for a drive unit for a hybrid vehicle and a method for operating the same, by means of which the starting of the internal combustion engine can be carried out from a purely electric drive out with greater comfort.

From the EP 1 612 440 A1 is a multi-plate clutch known that can be gradually closed. For this purpose, the multi-plate clutch preferably comprises corrugated springs running distance spring elements that allow a stepwise pressing together individual slats or groups of slats of the multi-plate clutch.

On this basis, the present invention based on the object to provide a novel drive unit for a hybrid vehicle and a method for operating the same. This object is achieved by a drive unit for a hybrid vehicle according to claim 1. According to the invention for starting the internal combustion engine at the transition from the purely electric drive in the hybrid ride the multi-plate clutch is gradually closable such that for the start of the engine only a subset of the inner disks and outer disks transmits a torque for starting the engine.

The invention enables a particularly comfortable starting of an internal combustion engine with purely electric drive of a hybrid vehicle. When starting the internal combustion engine, only a subset of the disks of the multi-plate clutch transmits the torque to be transmitted for starting. As a result, the internal combustion engine with respect to the output virtually no reaction and therefore not be noticeably started for a driver or passenger.

According to a first development, a first group of inner disks or a first group of outer disks are associated with first spring elements having a first, relatively large spring constants which counteract the closing of the multi-plate clutch, wherein a second group of inner disks or a second group of outer disks second spring elements with a second, relatively small spring constants are associated, which also counteract the closing of the multi-plate clutch, wherein for the start of the internal combustion engine, only the second group of inner disks and outer disks transmit the torque for starting the internal combustion engine. This embodiment, in which different spring elements are installed with different spring constants on the multi-plate clutch, has the advantage that in this case can be dispensed with a separate return element for the actuator.

According to a second, alternative development of a first group of inner disks or a first group of outer disks are associated with spring elements which counteract the closing of the multi-plate clutch, whereas a second group of inner disks or a second group of outer disks are assigned no such spring elements, wherein the states Internal combustion engine only the second group of inner disks and outer disks transmit the torque for starting the internal combustion engine. This development of the invention has the advantage that the same manages with a smaller number of modules, as only one group of slats corresponding spring elements are assigned.

Preferably, the spring elements are biased. With this configuration, a higher torque can be transmitted to the start of the engine.

The inventive method for operating the drive unit for a hybrid vehicle is defined in claim 6. To start the internal combustion engine, the multi-plate clutch on the pressurized actuator is gradually closed so that initially in a first phase by increasing the pressure on the actuator only a clearance between the inner disk or the outer disk of the second group is reduced, so that the multi-plate clutch initially transmits only a drag torque, and that then in a second phase by further pressure increase on the actuating element and a clearance between the inner disk or the outer disk of the first group is reduced so that on the second subset of inner disks or outer disks torque and the first subset of inner disks or outer disks a drag torque is transferable wherein the starting of the internal combustion engine takes place in the second phase. The inventive method allows a particularly comfortable starting of the internal combustion engine from an electric drive of the hybrid vehicle out.

Preferred developments emerge from the subclaims and the following description. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 an exemplary schematic of a drive unit for a hybrid vehicle;

2 a section of a drive unit according to the invention for a hybrid vehicle; and

3 an enlarged detail of the 2 ,

1 shows a schematic view of a drive unit 1 for a hybrid vehicle, wherein the drive unit 1 an internal combustion engine 2 , an electric machine 3 and a gearbox 4 includes. The gear 4 is between the internal combustion engine 2 or the electric machine 3 and a downforce 5 the hybrid vehicle switched.

Then, when the hybrid vehicle is purely electric, is the internal combustion engine 2 stopped or switched off and via an open multi-disc clutch 6 from the downforce 5 decoupled. In a hybrid ride is the multi-plate clutch 6 closed and therefore the internal combustion engine 2 to the output 5 coupled.

In the multi-plate clutch 6 it may be an internal gearbox or gearbox external multi-plate clutch.

The multi-plate clutch 6 is between a shaft of the internal combustion engine 2 and a shaft of the transmission 4 connected.

In addition, the gearbox has 4 further switching elements 7 which can be closed or opened to perform a gear change, wherein it is in the switching elements 7 can act positively as well as frictional switching elements.

2 shows a section of a drive unit according to the invention for a hybrid vehicle in the field of multi-plate clutch 6 , wherein the multi-plate clutch 6 according to 2 several on an outer disk carrier 8th recorded outer plates 9 as well as several on an inner disk carrier 10 recorded inner fins 11 includes.

To close the multi-plate clutch 6 are the outer plates 9 and the inner plates 11 compressible, namely via a pressurized actuator 12 , wherein it is in this pressurized actuator 12 preferably is an actuating piston. By increasing a pressure in a piston chamber 13 of the actuating piston 12 can therefore the slats 9 and 11 the multi-plate clutch 6 to close it to be compressed.

The pressurized closing of the multi-disc clutch 6 takes place counter to the restoring force of a return element 14 , which is preferably designed as a spring.

In order to comfortably start the combustion engine during the purely electric drive of the hybrid vehicle during the transition from the purely electric drive into the hybrid drive, the multi-plate clutch is 6 gradually closable, namely such that for the start of the internal combustion engine 2 only a subset of the inner disks and the outer disks transmits a torque for starting the internal combustion engine.

In the illustrated embodiment of the 2 and 3 are a first group 15 the inner plates 11 spring elements 16 associated with which the closing of the multi-plate clutch 6 counteract, whereas a second group 17 the inner plates 11 no such spring elements are assigned.

To start the internal combustion engine 2 out of a purely electric ride transmits only the second group 17 the inner plates 11 and outer plates 9 that for starting the internal combustion engine 2 required torque, whereas the first group 17 the inner plates 11 and outer plates 9 who has the spring elements 16 is assigned, for starting the internal combustion engine 2 no torque transfers, but at best a drag torque.

In contrast to the embodiment shown, the spring elements 16 also the outer lamellae 9 be assigned.

At the spring elements 16 are preferably corrugated springs.

In contrast to the embodiment shown, it is also possible that the first group 15 the inner plates 11 or the first group 15 the outer lamellae 9 first spring elements are associated with a first, relatively large spring constants, which closing the multi-plate clutch 6 counteract, and that of the second group 17 the inner plates 11 or the second group 17 the outer lamellae 9 second spring elements are associated with a second, relatively small spring constants, which closing the multi-plate clutch 6 counteract as well. The first spring elements have in comparison to the second spring elements on the relatively large spring constant.

For the start of the internal combustion engine transmitted in this case, only the fins 9 . 11 the second group 17 the torque for starting the internal combustion engine 2 ,

Although this variant of the invention requires a higher construction cost, this variant has the advantage that on a separate return element 14 (please refer 2 ) can be omitted, since then the first spring elements, the function of the return element 14 take over and provide the same.

Preferably, in the embodiment of 2 the spring elements 16 biased. Then, when the spring elements 16 are biased, must to compress the slats 9 and 10 the first group 15 not only the spring force of these spring elements but also the biasing force of the same are overcome. This can then for the engine start on the slats 9 . 11 the second group 17 a higher torque can be transmitted so that a higher torque range is available for the start of the internal combustion engine.

In the embodiment shown are the spring elements 16 each on the outer plates 9 the first group 15 and are above the corresponding inner fins 11 arranged.

In contrast, it is also possible that the spring elements 16 in each case on the inner disks of the first group 15 abut and then below the outer plates 9 are positioned.

Closing the multi-plate clutch 6 is subdivided depending on the on the actuator 12 acting pressure in preferably three phases.

In a first phase is by a corresponding relatively small increase in pressure on the actuator 12 initially only a clearance between the inner plates 11 and the outer plates 9 the second group 17 the multi-plate clutch 6 reduced, so that the multi-plate clutch 16 initially only a drag torque can be transmitted.

Subsequently, in a second phase by further pressure increase on the actuating element 12 also a clearance between the inner disks 11 and the outer plates 9 the first group 15 reduced, namely, when in the illustrated embodiment, the pressure increase is so great that the spring force of the spring elements 16 can be overcome. Then, when the spring elements 16 are biased, the pressure increase must be so great that the biasing force of the same can be overcome. In the second phase, therefore, the slats 9 . 11 the second group 17 transmit a torque, the fins 9 . 11 the first group 15 however, at most, a drag torque is transmitted.

In a third phase can by repeated pressure increase on the pressure element 12 the clearance on all slats 9 . 11 both groups 15 . 17 be reduced to zero, in which case the multi-plate clutch 6 is completely closed.

The starting of the internal combustion engine takes place in the second phase, that is, when the fins 9 . 11 the second group 17 are compressed and can transmit a torque, whereas the clearance on the slats 9 . 11 the first group 15 the multi-plate clutch 6 not yet reduced so much that they can transmit a torque.

The invention allows a comfortable starting of the internal combustion engine 2 from purely electrical drive of the hybrid vehicle out.

LIST OF REFERENCE NUMBERS

1

drive unit

2

internal combustion engine

3

electric machine

4

transmission

5

output

6

multi-plate clutch

7

switching element

8th

External disk carrier

9

outer plate

10

Inner disk carrier

11

inner plate

12

actuator

13

piston chamber

14

Return element

15

first group

16

spring element

17

second group

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2311680 A2 [0002]
• EP 1612440 A1 [0006]

Claims (7)

Drive unit for a hybrid vehicle, with an internal combustion engine ( 2 ), an electric machine ( 3 ) and a transmission ( 4 ), between a shaft of the internal combustion engine ( 2 ) and a shaft of the transmission ( 4 ) an internal gearbox or transmission-external multi-plate clutch ( 6 ) is switched, which when the internal combustion engine ( 2 ) is open during a purely electric drive of the hybrid vehicle and that is closed during a hybrid drive of the hybrid vehicle, wherein the multi-plate clutch ( 6 ) several inner disks ( 11 ) and several outer disks ( 9 ), which via a pressurized actuating element ( 12 ) against the restoring force of a restoring element ( 14 ) for closing the multi-plate clutch ( 6 ) are compressible, characterized in that for starting the internal combustion engine ( 2 ) in the transition from the purely electric drive of the hybrid vehicle in the hybrid drive of the hybrid vehicle, the multi-plate clutch ( 6 ) is closable in such a stepwise manner that for starting the internal combustion engine ( 2 ) only a subset of the inner plates ( 11 ) and outer plates ( 9 ) a torque for starting the internal combustion engine ( 2 ) transmits. Drive unit according to claim 1, characterized in that a first group of inner disks ( 11 ) or a first group of outer disks ( 9 ) are assigned first spring elements with a first, relatively large spring constant, which the closing of the multi-plate clutch ( 6 ), and that a second group of inner disks ( 11 ) or a second group of outer disks ( 9 ) second spring elements are associated with a second, relatively small spring constant, which the closing of the multi-plate clutch ( 6 ) counteract, wherein for the start of the internal combustion engine ( 2 ) exclusively the second group of inner disks ( 11 ) and outer plates ( 9 ) the torque for starting the internal combustion engine ( 2 ) transmits. Drive unit according to claim 2, characterized in that the first spring elements provide the restoring force of the return element and form the same. Drive unit according to claim 1, characterized in that a first group ( 15 ) of the inner disks ( 11 ) or a first group ( 15 ) of the outer disks ( 9 ) Spring elements ( 16 ) associated with the closing of the multi-plate clutch ( 6 ), whereas a second group ( 17 ) of the inner disks ( 11 ) or a second group ( 17 ) of the outer disks ( 9 ) no such spring elements are assigned, wherein for the start of the internal combustion engine exclusively the second group ( 17 ) of the inner disks ( 11 ) and outer plates ( 9 ) transmits the torque for starting the internal combustion engine. Drive unit according to claims 2 to 4, characterized in that the spring elements ( 16 ) are biased. Method for operating a drive unit for a hybrid vehicle according to one of claims 1 to 5, wherein for starting the internal combustion engine ( 2 ) the multi-plate clutch ( 6 ) via the pressurized actuating element ( 12 ) is closed in such a stepwise manner that initially in a first phase by increasing the pressure on the actuating element ( 12 ) only one clearance between the inner plates ( 11 ) or the outer plates ( 9 ) of the second group ( 17 ) is reduced, so that the multi-plate clutch initially only transmits a drag torque, and then in a second phase by further pressure increase on the actuating element ( 12 ) also a clearance between the inner plates ( 11 ) or the outer plates ( 9 ) of the first group is reduced so that over the second subgroup ( 17 ) of the inner disks ( 11 ) or outer plates ( 9 ) a torque and over the first subgroup ( 15 ) of the inner disks ( 11 ) or outer plates ( 9 ) a drag torque is transferable, wherein the starting of the internal combustion engine ( 2 ) in the second phase. A method according to claim 6, characterized in that after the start of the internal combustion engine ( 2 ) in the third phase by further pressure increase at the actuator ( 12 ) the clearance at all slats ( 9 . 11 ) of the multi-plate clutch ( 6 ) is reduced to zero.

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