Dual clutch transmission for a motor vehicle

Patent metadata

Field	Value
Publication number	US-10119595-B2
Application number	US-201514934290-A
Country	US
Kind code	B2
Filing date	Nov 6, 2015
Priority date	Nov 7, 2014
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

A dual-clutch transmission has first and second coaxial input shafts, the second shaft extending through the first shaft. The input shafts couple respective countershafts via input constants which have drive input and output wheels. The countershafts are selectively connectable, via spur gear stages that can be engaged by gearshift elements, to an output shaft. Four gear stages engage forward gears and one reverse gear stage engages reverse gears. The second and fourth gear stages are arranged between the first countershaft and the output shaft, and the other gear stages are arranged between the second countershaft and the output shaft. The first input constant has a higher gear ratio than the second input constant. The output of the first input constant is a loose wheel supported on the second countershaft and can couple the first countershaft by a first coupling element. A second coupling element couples the first and second countershafts.

First claim

The invention claimed is:

1. A dual-clutch transmission of a motor vehicle comprising:
a centrally arranged first input shaft and a second input shaft in the form of a hollow shaft being arranged coaxially over the first input shaft;
drive input sides of the first and the second input shafts each being connectable, by a respective friction clutch, to a driveshaft of a drive engine;
transmission sides of the first and the second input shafts being drivingly connectable, by way of a respective input constant, with a respective countershaft, and the input constants comprising a drive input wheel and a drive output wheel;
the first and the second countershafts being selectively drivingly connectable, via a plurality of spur gear stages each of which are engagable by a respective gearshift element, with an output shaft that is arranged coaxially with and axially adjacent to the first input shaft;
the first countershaft being a hollow shaft that is arranged coaxially over the second countershaft;
first, second, third and fourth spur gear stages engaging forward gears, gear ratios of the first, the second, the third and the fourth spur gear stages decrease with increasing order number, and one reversing spur gear stage engages reverse gears;
the second spur gear stage and the fourth spur gear stage being arranged between the first countershaft and the output shaft;
the first and the third spur gear stages and the reversing spur gear stage being arranged between the second countershaft and the output shaft;
the first input constant having a higher gear ratio than the second input constant;
the drive output wheel of the first input constant being a loose wheel, which is mounted to rotate on the second countershaft and being connectable, in a rotationally fixed manner, to the first countershaft by a first coupling shifting element; and
the first countershaft being connectable, in rotationally fixed manner, to the second countershaft by a second coupling shifting element.

2. The dual-clutch transmission according to claim 1 , wherein the first, the second, the third and the fourth, spur gear stages for the forward gears have a substantially geometric gear gradation; and
a gear ratio gradation of the input constants corresponds substantially to a square-root of the gear ratio gradation of the first, the second, the third and the fourth spur gear stages for the forward gears.

3. The dual-clutch transmission according to claim 1 , wherein the fourth spur gear stage is arranged axially adjacent to the first input constant; and
a loose wheel, of the fourth spur gear stage, is mounted to rotate on the output shaft and is connectable thereto in a rotationally fixed manner by a third coupling shifting element.

4. The dual-clutch transmission according to claim 3 , wherein the gear ratios of the input constants and of the first, the second, the third and the fourth spur gear stages for the forward gears are chosen such that,
a fifth gear, which is engagable by the third coupling shifting element and the gearshift element of the second spur gear stage, has a lower gear ratio than a fourth gear which is engagable by the second coupling shifting element and the gearshift element of the second spur gear stage, and a higher gear ratio than a sixth gear which is engagable by the gearshift element of the third spur gear stage; and
gear intervals between the fifth gear and the fourth and the sixth gears adjacent thereto correspond substantially to gear intervals of the other gears.

5. The dual-clutch transmission according to claim 3 , wherein the gear ratios of the input constants and of the first, the second, the third and the fourth spur gear stages are selected such that:
a direct gear, which is engagable by the third coupling shifting element and the gearshift element of the fourth spur gear stage, has a lower gear ratio than an eighth gear which is engagable by the second coupling shifting element and the gearshift element of the fourth spur gear stage; and
a gear interval between the direct gear and the eighth gear corresponds substantially to the gear gradation of the other gears.

6. The dual-clutch transmission according to claim 3 , wherein the loose wheel of the first input constant is connectable, in rotationally fixed manner, to the second countershaft by a fourth coupling shifting element.

7. The dual-clutch transmission according to claim 6 , wherein the gear ratios of the first and the second input constants and of the first, the second, the third and the fourth spur gear stages are selected such that:
a tenth gear, which is engagable by the third and the forth coupling shifting elements and the gearshift element of the fourth spur gear stage, has a lower gear ratio then a direct gear, which is engagable by the third coupling shifting element and the gearshift element of the forth spur gear stage; and
a gear interval between the tenth gear and the direct gear corresponds substantially to the gear gradation of the other gears.

8. The dual-clutch transmission according to claim 1 , wherein a loose wheel of the second spur gear stage is mounted to rotate on the output shaft, and the gearshift elements of the second and the fourth spur gear stages are combined in a double shifting element.

9. The dual-clutch transmission according to claim 1 , wherein the third spur gear stage is arranged axially adjacent to the second spur gear stage, a loose wheel of the third spur gear stage is mounted to rotate on the second countershaft, and the gearshift element of the third spur gear stage and the second coupling shifting element are combined in a double shifting element.

10. The dual-clutch transmission according to claim 1 , wherein the loose wheels of the first spur gear stage and the reversing spur gear stage are arranged together either on the output shaft or on the second countershaft, and the gearshift elements of the first spur gear stage and the reversing spur gear stage are combined in a double shifting element.

11. A dual-clutch transmission of a motor vehicle,
first and second input shafts, the second input shaft being a hollow shaft and the first input shaft being coaxial with and extending through the second input shaft;
an input side of the first input shaft being connectable, via a first friction clutch, to driveshaft of a drive engine, and an input side of the second input shaft being connectable, via a second friction clutch, to the driveshaft of the drive engine;
a transmission side of the first input shaft being connectable with a first countershaft via a first input constant which comprises a drive input wheel and a drive output wheel, the first countershaft being selectively drivingly connectable with an output shaft by a plurality of spur gear stages which are engagable by respective gear shifting elements, and the output shaft being coaxially aligned with and axially spaced from the first input shaft;
the second countershaft being selectively drivingly connectable with the output shaft by the plurality of spur gear stages which are engagable by the respective gear shifting elements, and the first countershaft being a hollow shaft and the second countershaft being coaxial with and extending through the first countershaft;
the plurality of spur gear stages comprising first, second, third and fourth spur gear stages which engage forward gears and a reverse spur gear stage which engages reverse gears, the first spur gear stage having a transmission ratio, the second spur gear stage has a transmission ratio that is lower than the transmission ratio of the first spur gear stage, the third spur gear stage having a transmission ratio that is lower than the transmission ratio of the secon

Assignees

• Zahnradfabrik Friedrichshafen

Inventors

• Schepperle Bernd

Classifications

• F16H3/093

  with two or more countershafts · CPC title

• F16H3/097 Primary

  the input and output shafts being aligned on the same axis · CPC title

• F16H2200/0086

  the gear ratios comprising two reverse speeds · CPC title

• F16H2003/0933

  with coaxial countershafts · CPC title

• F16H2200/0069

  the gear ratios comprising ten forward speeds · CPC title