The invention relates to a multi-stage transmission.
A multi-stage transmission is already known from DE 10 2011 108 024 A1 for a motor vehicle having a transmission input shaft for non-rotatable connection of an internal combustion engine, four planetary gear stages which are disposed one behind the other along a main axis of rotation, and a combined gear shift unit. In this case the gear shift unit is designed as a brake and has a rotatable coupling element as well as a friction-locking unit and a form-locking unit connected in parallel with the friction-locking unit, which are in each case provided to connect the rotatable coupling element fixedly to the housing. One of the planetary gear stages of the multi-stage transmission in DE 10 2011 108 024 A1 is associated with the combined gear shift unit and has a transmission element which is permanently non-rotatably connected to the rotatable coupling element of the combined gear shift unit.
Furthermore, a multi-stage transmission is known from the generic DE 10 2011 112 235 A1 in which additionally the planetary gear stage associated with the combined gear shift unit comprises a further transmission element which is permanently connected non-rotatably to the transmission input shaft.
The object of the invention is in particular to reduce any power loss of the multi-stage transmission without affecting the installation space.
The invention relates to a multi-stage transmission for a motor vehicle, having a transmission input shaft for non-rotatable connection to an internal combustion engine, having at least four planetary gear stages which are disposed one behind the other along a main axis of rotation and at least one combined gear shift unit which is configured as a brake and which has a rotatable coupling element as well as a friction-locking unit and a form-locking unit connected in parallel with the friction-locking unit, which are in each case provided in order to connect the rotatable coupling element fixedly to the housing, wherein one of the planetary gear stages is associated with the combined gear shift unit and comprises a transmission element which is permanently connected non-rotatably to the rotatable coupling element of the combined gear shift unit.
Furthermore, it is assumed that the planetary gear stage associated with the combined gear shift unit comprises a further transmission element which is permanently non-rotatably connected to the transmission input shaft. In this way a transmission element of a planetary gear stage configured as an input stage can be particularly advantageously connected frictionally and/or by form-locking non-rotatably to a transmission housing, so that by securing of the transmission element selectively engageable gears with different torque requirements can be shifted in a loss-optimized and convenient manner. Due to the association of the combined gear shift unit with the planetary gear stage, which has a transmission element permanently non-rotatably attached to the transmission input shaft, an installation space can be utilized better, so that the multi-stage transmission can be of particularly compact design. In this way a power loss, in particular a drag effect, of the multi-stage transmission can be reduced in particular without affecting the installation space, in particular without the provision of an additional installation space. “Additionally” should be understood in particular to mean additional by comparison with a multi-stage transmission which lacks a combined gear shift unit associated with a planetary gear stage configured as an input stage. A “gear shift unit configured as a brake” should in particular be understood as a gear shift unit which is disposed functionally between one of the planetary gear stages and the transmission housing and is provided in order, in a closed state, to connect the rotatable coupling element thereof non-rotatably to the transmission housing of the multi-stage transmission. In this context a “form-locking unit” should be understood in particular to be a part of the combined gear shift unit which for fixed connection to the housing has a tooth system and/or claws which interengage by form-locking in order to produce a non-rotatable coupling, such as in particular a claw-type gear shift unit. In this context a “friction-locking unit” should be understood in particular to be a part of the combined gear shift unit which for fixed connection to the housing has friction elements, such as in particular discs, which are connected to one another frictionally in order to produce a non-rotatable coupling, such as in particular a disc-type gear shift unit. The friction-locking unit and the form-locking unit are preferably functionally disposed between the transmission housing and the rotatable coupling element of the combined gear shift unit. “Non-rotatably connected” should in particular be understood to mean a connection in which a power flow averaged over a complete revolution is transmitted with an unchanged torque, an unchanged direction of rotation and/or an unchanged rotational speed. A “combined gear shift unit” should in particular be understood to be a gear shift unit which for production of a non-rotatable connection has a friction-locking unit and a form-locking unit connected in parallel with the friction-locking unit, wherein the non-rotatable connection can be produced by the friction-locking unit alone, by the form-locking unit alone or jointly by the friction-locking unit and the form-locking unit. A “planetary gear stage associated with the combined gear shift unit” should be understood to be a planetary gear stage which has at least one transmission element which is permanently non-rotatably connected to the rotatable coupling element of the combined gear shift unit. A “planetary gear stage designed as an input stage” should be understood in particular to be a planetary gear stage having at least one transmission element which is permanently connected non-rotatably to the transmission input shaft. “Provided” should be understood in particular to mean specially programmed, equipped, configured and/or disposed.
According to the invention it is proposed that the form-locking unit is disposed radially inside the friction-locking unit, so that a circumferential speed of a form-locking tooth system of the form-locking unit can be kept low. The term “radially” and the term “radius” relate in particular to the main axis of rotation, so that the expression “radially” designates a direction which extends perpendicular to the main axis of rotation. A “form-locking unit disposed radially inside the friction-locking unit” should in particular be understood to be a form-locking unit of which the tooth system and/or claws run around a circular path having an average diameter which is smaller than an average diameter of a circular path on the friction surfaces of the friction elements.
Furthermore, it is proposed and assumed that the transmission element, which is permanently connected non-rotatably to the transmission input shaft, of the planetary gear stage associated with the combined gear shift unit is configured as a sun gear. As a result a driving torque provided by the internal combustion engine can be advantageously introduced into the multi-stage transmission via the planetary gear stage associated with the combined gear shift unit.
Furthermore, it is proposed that the transmission element, which is permanently connected non-rotatably to the rotatable coupling element of the combined gear shift unit, of the planetary gear stage associated with the combined gear shift unit is configured as a planetary gear support, so that the planetary gear stage configured as an input stage can be advantageously connected.
In particular it is advantageous if the planetary gear stage associated with the combined gear shift unit has a transmission element which is configured as a ring gear and can at least be connected non-rotatably to a transmission element of at least one other planetary gear stage, so that the connection of the planetary gear stage associated with the combined gear shift unit can be further improved. The expression “can at least be connected” should be understood in particular to mean that the connection can either be produced by a gear shift unit or is produced permanently.
Furthermore, it is advantageous if the rotatable coupling element of the combined gear shift unit can at least be connected non-rotatably to a transmission element of at least one of the other planetary gear stages, so that the combined gear shift unit can act on at least one further planetary gear stage.
Furthermore, it is advantageous if the multi-stage transmission has a housing end wall on the drive side, wherein the planetary gear stage associated with the combined gear shift unit is disposed immediately adjacent to the housing end wall on the input side with respect to the other planetary gear stages. In this way the planetary gear stage associated with the combined gear shift unit can be disposed on the input side, so that the combined gear shift unit can be associated with the planetary gear stage configured as an input stage without affecting the installation space. A “housing end wall on the drive side” should in particular be understood to be a housing end wall which, by comparison with an axially opposing housing end wall on the output side, is disposed closer to the internal combustion engine axially and/or along a flux of force emanating from the internal combustion engine. The expression “disposed immediately adjacent to the housing end wall on the input side with respect to the other planetary gear stages” should in particular be understood to mean that a planetary gear stage is absent axially between the housing end wall on the drive side and the planetary gear stage associated with the combined gear shift unit. The expression “axially” relates in particular to the main axis of rotation, so that the term “axially” designates a direction which extends on the main axis of rotation or parallel thereto.
In an advantageous configuration the friction-locking unit and/or the form-locking unit of the combined gear shift unit are disposed axially between the housing end wall on the drive side and the planetary gear stage associated with the combined gear shift unit, so that a particularly compact multi-stage transmission can be provided.
It is particularly advantageous if the form-locking unit of the combined gear shift unit is disposed axially between the friction-locking unit and the planetary gear stage associated with the combined gear shift unit, so that the form-locking unit can be configured in a particularly space-saving manner.
It is advantageous to place the form-locking unit on a small radius. Where appropriate the form-locking unit can be disposed on the same radius as the friction-locking element.
Furthermore it is proposed that the multi-stage transmission comprises a further gear shift unit which is configured as a clutch and has a rotatable coupling element which is permanently connected non-rotatably to the transmission input shaft and an outer disc support which is configured at least partially integrally with an inner disc support of the friction-locking unit of the combined gear shift unit. In this way a space-saving design of the combined gear shift unit and the further gear shift unit can be realized. A “gear shift unit configured as a clutch” should in particular be understood to be a gear shift unit which is provided in order that the two rotatably disposed coupling elements thereof, which are rotatable independently of one another in an opened state, can be connected non-rotatably to one another in a closed state. A gear shift unit configured as a clutch is preferably disposed in a flux of force between at least two planetary gear stages. “Integrally” should in particular be understood to mean formed in one piece, such as for example by production from a casting. The outer disc support and the inner disc support configured integrally with the outer disc support are preferably provided in order to accommodate inner discs of the friction-locking unit of the combined gear shift unit and to accommodate outer discs of a friction-locking unit of the further gear shift unit.
In particular it is advantageous if the form-locking unit of the combined gear shift unit is disposed axially between the housing end wall on the drive side and the further gear shift unit, so that an alternative arrangement of the form-locking unit can be provided.
Furthermore, it is advantageous if the combined gear shift unit has a first actuating unit provided for actuating the friction-locking unit as well as a second actuating unit provided for actuating the form-locking unit and the further gear shift unit has a third actuating unit, wherein the first actuating unit and the third actuating unit are disposed axially between the housing end wall on the drive side and the second actuating unit. In this way an advantageous actuation of the combined gear shift unit and the further gear shift unit can be achieved without the provision of additional installation space.
In an alternative embodiment it is advantageous if the combined gear shift unit has a first actuating unit provided for actuating the friction-locking unit as well as a second actuating unit provided for actuating the form-locking unit and the further gear shift unit has a third actuating unit, wherein the first actuating unit, the second actuating unit and the third actuating unit are disposed axially between the housing end wall on the drive side and the friction-locking unit of the combined gear shift unit. In this way the form-locking unit of the combined gear shift unit can be disposed radially inside the friction-locking unit of the combined gear shift unit and radially inside a friction-locking unit of the further gear shift unit, so that the circumferential speed of the form-locking tooth system can be further reduced. Furthermore, it may also be provided that closing directions of the actuating units are all aligned, so that a supply of an actuating medium to the actuating units for closing the friction-locking units and the form-locking unit can be simplified. A “closing direction” should in particular be understood to be a direction in which an actuating element of the actuating unit must be moved in order to close the friction-locking unit or the form-locking unit. In this context “oriented in the same direction” should in particular be understood to mean that the closing directions point in the same direction. An “actuating element” should in particular be understood to be an axially movable element which presses the inner and outer discs of a friction-locking unit against one another for closing the friction-locking unit or moves a form-locking tooth system of a form-locking unit into a corresponding form-locking tooth system of the form-locking unit for closing the form-locking unit.
In a further alternative embodiment it is advantageous if the combined gear shift unit has a first actuating unit provided for actuating the friction-locking unit as well as a second actuating unit provided for actuating the form-locking unit and the further gear shift unit has a third actuating unit, wherein the second actuating unit and the third actuating unit are disposed axially between the housing end wall on the drive side and the first actuating unit. In this way the form-locking unit of the combined gear shift unit can be disposed radially inside the friction-locking unit of the further gear shift unit in particular without affecting the installation space.
Moreover, it is advantageous if, with respect to an axial succession starting from the internal combustion engine, the planetary gear stage associated with the combined gear shift unit is configured as a first planetary gear stage and a planetary gear stage adjacent to the planetary gear stage associated with the combined gear shift unit is configured as a second planetary gear stage, wherein the adjacent planetary gear stage has a transmission element which is configured as a planetary gear support and is permanently connected non-rotatably to a transmission element, configured as a ring gear, of the planetary gear stage associated with the combined gear shift unit, and has a transmission element which is configured as a ring gear and is permanently connected non-rotatably to a transmission element, configured as a sun gear, of a third planetary gear stage and to a transmission element, configured as a sun gear, of a fourth planetary gear stage and can also be connected non-rotatably to the transmission element, configured as a planetary gear support, of the planetary gear stage associated with the combined gear shift unit. In this way a particularly advantageous interconnection of the planetary gear stages can be realized. With respect to the axial succession of the planetary gear stages along an axial direction starting from the internal combustion engine, the first planetary gear stage is disposed in the first place, the second planetary gear stage is disposed in the second place, the third planetary gear stage is disposed in the third place and the fourth planetary gear stage is disposed in the fourth place. A “planetary gear stage adjacent to the planetary gear stage associated with the combined gear shift unit” should be understood to be a planetary gear stage which is disposed axially next in the sequence to the planetary gear stage associated with the combined gear shift unit.
The configuration of a multi-stage transmission described below constitutes a special exemplary embodiment, for which in principle there are further kinematically equivalent exemplary embodiments. For example in particular the planetary gear stages can be formed by means of single planetary gear sets, as is set out below. However, in a kinematically equivalent manner one of the planetary gear stages can also have a double planetary gear set, so that for the same mode of action only one stationary gear ratio of the planetary gear stage must be adapted. Moreover, a connection of a sun gear and a planetary gear support or of a ring gear and a planetary gear support can also be changed, without the kinematics of the multi-stage transmission changing.
Further advantages can be seen from the following description of the drawings. Four exemplary embodiments of the invention are shown in the drawings. The drawings, the description of the drawings and the claims contain numerous features in combination. Expediently, the person skilled in the art will also consider the features singly and combine them to form meaningful further combinations.