DE19918734A1 - Variable speed transmission for motor vehicles has first and second power transmission clutches brought into functional communication via transmission constant with output shaft with stepping up of lowest gear speed for starting - Google Patents

Abstract

The first(K1) and second(K2) power transmission clutches of the gearbox through a transmission constant(C1) are each brought into functional communication, which may be simultaneous, with the output shaft(20) with a stepping up of the lowest gear speed for starting. At least the transmission constant allocated to the lowest gear speed communicates with the first and second clutch. Both clutches for starting may be brought into functional communication with the output shaft through the same transmission constants and the same gearwheel pair. An Independent claim is included for a procedure for changing gear in which the first, second or both clutches together can be used for starting depending upon the running parameters.

Description

The invention relates to a gear change transmission with two partial gears arranged parallel to each other in the power flow according to the preamble of claim 1 and a method for Switch such gear change gear.

The manual transmission prevailing in motor vehicles with a friction clutch are simple and robust, but have that Disadvantage that a traction interruption during gear change chung occurs. Conventional automatic transmission with a hy drodynamic converters avoid an interruption in tractive force during the gear change, but due to the Converter a poorer efficiency than manual transmission be. Furthermore, they have a higher weight and are inexpensive more intensive.

For gear change transmissions with two frictional loads clutches and two parallel to each other in the power flow Orderly partial transmissions can change gears under load be performed, with an overlap control the power shift clutches. This allows inexpensive automa be achieved with a good efficiency. In As a rule, the straight transmission gears are the one partial transmission be and the odd gears the other sub-transmission assigned so that they are switched sequentially under load  can, but not easily over individual gears can be jumped, so-called double upshift or Double downshift.

From US 4,658,663 is a generic gear change gearbox known. In the gear change transmission is one Input shaft with an output shaft through a first and a second sub-gearbox connected in parallel to the power flow are arranged one above the other and each has a frictional load have switching clutch. With the power shift clutches Intermediate shafts of the sub-assemblies arranged concentrically to one another drives can be connected to the input shaft. The intermediate waves are about gear constants, about a common, parallel lay shaft arranged over the input shaft and over tooth Effectively connect wheel pairs to the output shaft. The Gear pairs for the forward gears I, III, and IV see above like the pair of gears for the reverse gear belong to that first partial transmission. The fourth gear is as direct ter gear and designed by engaging a Switching element between the output shaft and the intermediate shaft le of the first sub-transmission can be switched.

The second sub-transmission includes the gear pairs of the Vor upward gears II and V and an additional pair of gears, de ren translation equal to the translation of the third gear is gear, the gear pair of the first sub-gearbox hear. In the first part of the transmission is a gear coupling for the third gear and the direct clutch for the fourth Gear to an interchangeable clutch with a common Shift sliding sleeve summarized, which with a loose wheel of Gear pairs for the third gear or with the off gear shaft can be coupled.  

The powershift clutches of the partial transmissions are the transmissions corridors assigned alternately. To start from the first Gear is always the first powershift clutch of the he Most used sub-transmission, whereby on this compared to the second power shift clutch, increased wear occurs.

The invention has for its object a generic To further develop gear change transmissions and in particular longer maintenance intervals, less wear and tear to achieve greater security. It is according to the inven solved by the features of the independent claims. Further refinements result from the subclaims.

The invention is based on a gear change transmission which an input shaft with an output shaft through a he stes and a second sub-transmission is connected, which is in force are arranged parallel to each other. The partial transmissions be a frictional power shift clutch and one each Intermediate shaft, with the intermediate shaft in each case via the load the clutch can be effectively connected to the input shaft is. Furthermore, the gear change transmission has at least one ne first gear constant.

It is proposed that the first powershift clutch over a transmission constant and the second powershift clutch a gear constant with a ratio of the lowest Gearbox for starting with the output shaft in active binding can be brought. Both power shift clutches can be used for the starting process from the lowest or first gear be used. The Bela resulting from the starting process can be distributed to both power shift clutches. Egg ne excessive temperature can despite dimensio avoidance of wear, reduced wear and maintenance-in  tervalle can be extended. Furthermore, in the event of failure a powershift clutch, the second powershift clutch for on drive from the first gear and used the mobility security can be increased. Powershift is also possible Couplings different for different start-up processes to interpret.

The solution according to the invention can be used when changing gears drives are used, in which the intermediate shafts over at least one countershaft and at least one gear pair is connected to an output shaft. In addition, the inventor Solution according to the invention also in a gear change transmission be used in which the intermediate shafts with at least a transmission constant directly with at least one output wave are connected. Gear change transmission with a front lay waves are usually used in motor vehicles with a rear end drive and gear change gearbox without countershaft usually turned on in front-wheel drive vehicles puts.

The first and second loads are particularly advantageous clutch at the same time as the translation of the low Verify most transmission gear with the output shaft bindable. The power shift clutches can be particularly ko be inexpensive and easily dimensioned.

The solution according to the invention can by various, the subject achievements that appear to be suitable can be reached, for example with two identical gear constants, where egg ne gear constant of the first and a gear constant of the is assigned to the second intermediate shaft and via the transmission con ate, at least one countershaft and one ge common gear pair or via two identical gear pairs  an output shaft can be driven off or by over two identical gear constants directly to at least one off gear shaft can be driven off. Furthermore, with under different gear constants due to different tooth wheel pairs two first gear gears are created.

However, at least the lowest is particularly advantageous Gear constant associated with the first and the second powershift clutch can be brought into operative connection. It can both powershift clutches on the same transmission constant and over the same gear pair with the output shaft can be connected. Additional gear pairs, weight and Construction space as well as assembly effort and costs can be saved and due to its light weight and low rotating mass high efficiency can be achieved. Furthermore, the Powershift options increased and with a small number of gear pairs in addition to sequential switching at least the most important double upshifts and double downshifts conditions under load. Double upshifts and Double downshifts are particularly before and after a Overtaking required.

For various reasons, it can be useful instead of using the first gear with the second or even higher to start their gearbox, for example when starting slowly drive with an internal combustion engine with great performance when Starting off on slippery surfaces, on a slope and / or on Starting off with little or no load weight etc.

Especially when starting from a higher gear high loads occur on a powershift clutch. Around a resulting one-sided burden and an increased The first powershift is advantageous to avoid wear  coupling via a gear constant and the second load clutch via a gearbox constant to start with a translation of the second lowest gear or second gear with the output shaft in operative connection bringable. In principle, it is also conceivable that both loads clutches for starting with a ratio of one more ver higher gear ratio with the output shaft are binding.

Are the first and the second powershift clutch at the same time with the translation of the second gear with the off gearshift can be connected in terms of effectiveness, the powershift couplings are particularly inexpensive and lightly dimensioned become.

A simultaneous connection can thereby advantageously be made possible light that a gear on the first intermediate shaft first gear constant is arranged and on the second Intermediate shaft a gear from at least a second gear is arranged constant and the first intermediate shaft over a switching element arranged between the gears and via the second gear constant with the output shaft in Active connection can be brought. Additional gear pairs, installation space and costs can be saved.

Is a pair of gears the first and the second gear assigned, a pair of gears can be started from the first and used to start from the second gear and ent be dimensioned accordingly. Furthermore, especially in a neutral position, the switching elements for the second Ge drive gear can be selected so that after starting from the first gear by overlap control alone the powershift clutches from the first to the second transmission  gear can be switched. Which takes place under mostly high load Finding gear changes from the first to the second gear can be carried out particularly comfortably.

In an embodiment according to the invention, it is proposed that that the intermediate shaft of the first sub-transmission on the first Gearbox constant with one parallel to the input shaft th countershaft is connectable, which via at least one gear pair associated with the first partial transmission with the off gear shaft is operatively connectable, and that the first Ge drive constant either with the first, the second or with two power shift clutches can be brought into operative connection. In addition to using both power shift clutches for starting from the first gear via the first gear constant can be an advantageous gear arrangement with a small Number of gear pairs and with a high number of loads switching options can be achieved in which in addition to a se the most important double upshifts and Double downshifts are possible under load.

Is the output shaft through an engaging and disengaging switch element to form a direct gear with the Zwi connecting shaft of the first sub-transmission can be connected partly through the switchable second countershaft three Torque paths created between the input and output shaft become. The torque paths can be used alternately and in particular, a double downshift from the direct Gear and a double upshift to the direct Ge drive under load without an additional pair of gears become.

A space-saving gear change transmission can also be used few gear pairs and a high number of powershift options  options, especially with double upshift and double downshift Possibilities under load can be achieved by next to the he at least gear constant on the first intermediate shaft a different second gear constant on the two th intermediate shaft is arranged and at least one gear constant across both countershafts with the output shaft in Active connection can be brought. It can consist of several gears alternatively with the first, the second or with both Power shift clutches are started. Particularly advantageous every transmission constant is effective with every countershaft moderately connectable, so that every pair of gears with every gear constant can be brought into operative connection. Every tooth wheels can pair at least two gears or with more than two gear constants assigned more than two gear speeds become.

In an advantageous embodiment for a wide range of users In addition to two gear constants, the range of application also includes three teeth wheel pairs for six different forward gears and one Gear pair arranged for at least one reverse gear net. A gear of the fourth and sixth gear to ordered gear pair is on the second countershaft and a gear of the third and fourth gear assigned neten gear pair and a gear of the first and second Gear pair assigned to gear is on the first front lay shaft arranged.

An advantageous variant is also that a tooth wheel of the third and sixth gear assigned Gear pairs on the second countershaft and a gear of the second and fourth associated gear pair and a Gear wheel of the gear pair assigned to the first and second is arranged on the first countershaft. It can be beneficial  a first gear with a high gear ratio be enough, for example for use in a distillery Engine with a turbocharger, at an internal combustion engine machine with low power, in an off-road vehicle etc.

The powershift clutches are advantageously dependent on at least one operating parameter individually or together to the on drive used. In one embodiment it is proposed that the differential speed at least at one, advantageously at the power shift clutches and the power to be transmitted summarizes and depending on the differential speed and the carrying power the power shift clutches individually or ge can be used together to start off. With a big difference speed with high power are advantageous both powershift clutches used. Will with a low Differential speed approached can only with the first or be started with the second powershift clutch, which for different loads can be designed differently can. The powershift clutches can be particularly inexpensive stig and light dimensions and with little wear be driven.

The weight of the motor vehicle, including sive charge and / or the slope of a route of the force vehicle detected and depending on weight and / or incline the power shift clutches individually or together for starting be used. When starting on a steep incline and / or with a large load, both loads will be advantageous clutches used for starting.

The temperature of the powershift clutch usually increases the wear too. To reduce wear, it will  according to the invention at least on one, advantageously on both loads clutches detects the temperature. From dependent on the temperature of the power shift clutches used them individually or together to start off. The increases Temperature of a powershift clutch above a certain value , for example by frequent starting in a traffic jam a high ambient temperature, the powershift clutch alternately or shared. The warmers gie can be advantageous on both powershift clutches leads to an increased temperature only with a powershift clutch tion can be avoided and wear can be reduced.

In order to achieve the longest possible maintenance intervals, struck that the wear on the power shift clutches he and the power shift clutches depending on wear can be used individually or together to start off the power shift clutches are turned on for starting sets that at least to a certain extent the powershift clutches wear equally poses. Only when both powershift clutches largely ver are worn out, they must be replaced. It can particularly long maintenance intervals can be achieved. Further can advantageously both powershift clutches during maintenance exchanged together and labor and costs be saved.

To avoid having both powershift clutches at the same time are completely worn out and fail at the same time advantageous from a certain wear only one of the used two power shift clutches for starting. It will be one Kind of safety buffer created so that a driver after the Failure of a power shift clutch certainly not with that completely worn clutch to the nearest workshop  is coming. The driver is advantageously displayed that for the To only a power shift clutch is used. This allows him to adjust his driving behavior accordingly can visit a workshop in good time.

Further advantages result from the following drawing spelling. In the drawing, an embodiment of the Invention shown. The description and the claims ent keep numerous features in combination. The specialist will expediently also consider and consider the features individually summarize other useful combinations.

It shows:

Fig. 1 is a schematic representation of a drive gears Wech Selge in the neutral position,

Fig. 2, a change-speed gearbox according to Fig. 1 clutch during start from the first transmission gear with a first load,

Fig. 3 shows a gear change transmission according to Fig. 1 clutch when starting from the first gear to a second load,

Fig. 4, a change-speed gearbox according to Fig. 1 lungs when starting from the first transmission gear with both Lastschaltkupp,

Fig. 5 shows a gear change transmission according to FIG. 1 when starting from the second gear with both powershift couplings and

Fig. 6 shows an overview of possible gear changes.

Fig. 1 shows an inventive gear change transmission in which an input shaft 10 to an output shaft 20 through a first gear train 22 and a second partial transmission 24 which are arranged in the power flow parallel to each other. The partial transmissions 22 , 24 each have a frictional powershift clutch K1, K2 and an intermediate shaft 12 , 14 . The intermediate shafts 12, 14 are concentric with each other and arranged coaxially with the input shaft 10 and can in each case on the power-shift clutch K1, K2 to the input shaft 10 will be connected effect.

The first intermediate shaft 12 of the first partial transmission 22 is on the one hand with the output shaft 20 through an engaging and disengageable gear clutch S2 to form a direct fifth gear transmission V and on the other hand through the gear clutch S2 via a first gear constant C1 with a parallel to the output shaft 20 , As a hollow shaft countershaft 18 operatively connected.

The countershaft 18 of the first partial transmission 22 is connected by a gear pair ZIV / VI to form the highest and the second highest transmission gears IV, VI with the output shaft 20 . The gearwheel pair ZIV / VI has a fixed gear 52 which is connected in a rotationally fixed manner to the output shaft 20 and which meshes with a loose gear 30 . The idler gear 30 is concentrically and rotatably disposed on the front of clutch shaft 18 and be coupled to the countershaft 18 by an engageable and disengageable clutch gear S5. In the fixed gear 56 , the intermediate shaft 12 is mounted, which in particular special length can be saved.

Furthermore, the countershaft 18 of the first partial transmission 22 can be connected to the output shaft 20 via a gear pair ZIII / IV to form the third and fourth transmission gears III, IV. The gear pair ZIII / IV has a fixed gear 36 which is arranged concentrically and non-rotatably on the output shaft 20 and an idler gear 32 which is arranged concentrically and rotatably on a further countershaft 16 parallel to the output shaft 20 . The idler gear 32 can be coupled to the countershaft 18 via the gear clutch S5 that can be engaged and disengaged, and to the countershaft 16 using a gear clutch S6.

The second intermediate shaft 14, formed as a hollow shaft, of the second partial transmission 24 is connected via a second transmission constant C2 to the countershaft 16 , which passes through the countershaft 18 of the first partial transmission 22 with play. The second transmission constant C2 has a on the intermediate shaft 14 concentrically and rotatably disposed idler wheel 28, which is coupled with the intermediate shaft 14 via a gear clutch S1, and the countershaft 16 concentrically and rotatably connected to fixed gear 38th The countershaft 16 belonging to the second sub-gear 24 is via the gear pair ZIII / IV for the third and fourth gear III, IV, via a gear pair ZI / II for the first and second gear I, II and via a gear pair ZR for two reverse gears R. the output shaft 20 connected.

The gear pair ZI / II for the first and second gear I, II has a concentrically and rotatably arranged idler gear 40 on the output shaft 20 , which can be coupled with a gear coupling S3 with the output shaft 20 , and one on the countershaft 16 concentrically and fixed gear 34 arranged in a rotationally fixed manner.

The gear pair ZR for the reverse gears R has a on the output shaft 20 concentrically and rotatably angeord scribed idler gear 42, the clutch by the engageable and disengageable gear S3 is coupled with the output shaft 20, and a fixed gear 44, the concentric and rotationally fixed to the countershaft shaft 16 is connected. Between the idler gear 42 and the fixed gear 44 of the gear pair ZR a not shown gear is arranged for reversing the direction of rotation.

The first gear constant C1 has a fixed gear 46 arranged concentrically and non-rotatably on the countershaft le 16 , which meshes with an idler gear 26 arranged concentrically and rotatably on the intermediate shaft 12 of the first partial gear 22 . The idler gear 26 can be connected by the engaging and disengaging gear coupling S2 to the intermediate shaft 12 of the first sub-gear 22 and by the gear coupling S1 to the intermediate shaft 14 of the second sub-gear 24 . The second load clutch K2 or the second intermediate shaft 14 is thereby connected in addition to the second gear constant C2 with the first gear constant C1 effective. The first constant gear C1 can be brought into operative connection with the first, the second or with both powershift clutches K1, K2 through the gear clutches S1 and S2.

Furthermore, the intermediate shaft 14 of the second sub-gear 24 via the second gear constant C2 through an on and off shiftable gear clutch S4 with the fixed gear 46 of the gear constant C1 and thus with the countershaft 18 of the first sub-gear 22 and assigned to the first sub-gear 22 Gear pair ZIV / VI with the output shaft 20 are connected in terms of effectiveness. The intermediate shaft 12 can be via the first gear constant C1 advantageously by the on and off shiftable gear coupling S4 with the countershaft 16 and via the gearbox pairs ZIII / IV, ZI / II, ZR assigned to the second partial gear 24 with the output shaft 20 effectively connected . With each gear constant C1 and C2 can be driven to the output shaft 20 via each gear pair ZI / II, ZIII / IV, ZIV / VI, ZR. The transmission constants C1 and C2 are different, so that each gear pair ZI / II, ZIII / IV, ZIV / VI, ZR is assigned two transmission gears.

Fig. 2 shows the gear change transmission during the starting process from the first gear I with the first powershift clutch K1. The powershift clutch K1 is closed, the gear clutch S2 couples the idler gear 26 of the first gear constant C1 with the intermediate shaft 12 , the gear clutch S4 couples the gear constant C1 with the countershaft 16 and the gear clutch S3 couples the idler gear 40 of the gear pair ZI / II for the first and second gear I, II with the output shaft 20th The power flow runs from the input shaft 10 , via the powershift clutch K1, the intermediate shaft 12 , the gear clutch S2, the gear constant C1, the gear coupling S4, the countershaft 16 , the gear pair ZI / II and via the gear clutch S3 to the output shaft 20 .

The idler gear 28 of the second gear constant C2 is coupled to the intermediate shaft 14 by the gear coupling S1. The second gear II is preselected and can be shifted particularly comfortably only by an overlap control or by closing the second powershift clutch K2 and by opening the first powershift clutch K1 under load.

Fig. 3 shows the gear change transmission during the starting process from the first gear I with the second powershift clutch K2. The powershift clutch K2 is closed, the gear clutch S1 couples the intermediate shaft 14 to the idler gear 26 of the first gear constant C1, the gear clutch S4 couples the gear constant C1 to the countershaft 16 and the gear clutch S3 couples the idler gear 40 of the gear pair ZI / II to the Output shaft 20 . The power flow runs from the input shaft 10 , via the second powershift clutch K2, the intermediate shaft 14 , the gear coupling S1, the gear constant C1, the gear coupling S4, the countershaft 16 , the gear pair ZI / II and via the gear coupling S3 to the output shaft 20 .

Fig. 4, the gear shift transmission is during the starting from the first gear I with the first and second power-shift clutch K1, K2. The powershift clutches K1, K2 are closed, the gear clutch S1 couples the intermediate shaft 14 and the gear clutch S2 couples the intermediate shaft 12 to the idler gear 26 of the transmission constant C1. The gear clutch S4 couples the gear constant C1 to the countershaft 16 and the gear clutch S3 couples the idler gear 40 of the gear pair ZI / II to the output shaft 20 . The power flow runs from the input shaft 10 via the powershift clutches K1, K2, via the intermediate shafts 12 , 14 , via the gear coupling S1, S2, the gear constant C1, the gear coupling 54 , the countershaft 16 , the gear pair ZI / II and via the gear coupling S3 to output shaft 20 . If the differential speed in the powershift clutches K1, K2 drops to zero, the powershift clutch K2 is opened.

Both powershift clutches K1 and K2 are effectively connectable to start with the output shaft 20 via the same gear constant C1 and the same gear pair ZI / II. The first and second powershift clutches K1, K2 can be used individually or together for starting from the first gear I depending on operating parameters. If only the second powershift clutch K2 is started up from the first gear I, it can be shifted to the powershift clutch K1 without interruption of the tractive force or directly with the interruption of traction in the second gear II.

Fig. 5 shows the gear change transmission when starting from the second gear II with two Lastschaltkupplun gene K1, K2. Both powershift clutches K1, K2 are closed, the gear clutch S2 couples the idler gear 26 of the first gear constant C1 to the intermediate shaft 12 , the gear clutch S1 couples the idler gear 26 to the first gear constant C1 and the idler gear 28 of the second gear constant C2 to the intermediate shaft 14 . Gear clutch S3 couples idler gear 40 of gear pair ZI / II to output shaft 20 . The power flow runs from the input shaft 10 via the powershift clutches K1, K2, the intermediate shafts 12 , 14 , the gear coupling S1, S2, the gear constant C2, the countershaft 16 , the gear pair ZI / II and via the gear coupling S3 to the output shaft 20 . The gear coupling S1 consists of two parts 48 , 50 which are connected to one another and can be moved one inside the other. Furthermore, various constructions which appear sensible to a person skilled in the art are possible, in which the two loose wheels 26 , 28 of the transmission constants C1, C2 can be effectively connected to the intermediate shaft 14 .

In Fig. 6 is an overview of possible gear changes under load each from a source gear Q to a target gear Z Darge provides. The possible gear changes are marked with an X. The switched gear clutches are listed under GS. In addition to a neutral position of the gear clutch, two switching positions are possible, the coupled gear constant or the coupled gear pair is mentioned in each case to the gear coupling. With the two gear constants C1 and C2 and the three gear pairs ZI / II, ZIII / IV, ZIV / VI, six different forward gears I, II, III, IV, V, VI can be reached, the first gear I _1.2 twice , the third gear III _1.2 twice and the fourth gear IV _1.2.3 occurs three times.

Of the transmission gears I ₁ , III ₁ , V can be switched with an overlap control from the powershift clutch K1 to K2 sequentially under load in the transmission gears II, IV ₁ , VI and vice versa. Important double upshifts and double downshifts under load are also possible, namely double downshifts from VI to IV ₂ , from V to III ₂ , from IV ₂ to II and double upshifts, from II to IV ₂ , from III ₂ to V and from IV ₂ to VI. In addition, other multiple circuits marked with an X are possible under load.

Before shifting from fourth gear IV _1,2,3 to a target gear, fourth gear IV _1,2,3 under load is always selected from which shifting to target gear under load is possible. The same applies to the third gear III _1.2.

Claims (21)

1. Gear change transmission, in which an input shaft is connected to an output shaft by a first and a second part gear, which are arranged parallel to one another in the power flow and each have a frictional powershift clutch and an intermediate shaft, each having the intermediate shaft via the powershift clutch the input shaft is operatively connectable, and with at least a first transmission constant, characterized in that the first powershift clutch (K1) via a transmission constant (C1) and the second powershift clutch (K2) via a transmission constant (C1) each with a ratio of the lowest rigidity Gear (I) for starting with the output shaft ( 20 ) can be brought into operative connection. 2. Gear change transmission according to claim 1, characterized in that the first and the second power shift clutch (K1, K2) can be brought into operative connection with the output shaft ( 20 ) simultaneously with the transmission ratio of the lowest gear (I). 3. Gear change transmission according to one of the preceding An claims, characterized, that at least the one assigned to the lowest gear (I) Gearbox constant (C1) with the first and the second load switching clutch (K1, K2) can be brought into operative connection. 4. Gear change transmission according to claim 3, characterized in that both powershift clutches (K1, K2) for starting via the same gear constant (C1, C2) and via the same gear pair (ZI / II) with the output shaft ( 20 ) can be brought into operative connection . 5. Gear change transmission according to the preamble of claim 1 or according to one of the preceding claims, characterized in that the first powershift clutch (K1) via a transmission constant (C2) and the second powershift clutch (K2) via a transmission constant (C2) for starting with a Gear ratio of the second lowest gear (II) can be brought into operative connection with the output shaft ( 20 ). 6. Gear change transmission according to one of the preceding claims, characterized in that the first and the second powershift clutch (K1, K2) can be brought into operative connection with the output shaft ( 20 ) simultaneously with the transmission of the second lowest transmission gear (II). 7. Gear change transmission according to claim 6, characterized in that on the first intermediate shaft ( 12 ) a gear ( 26 ) of which he is the most constant gear (C1) is arranged and on the two th intermediate shaft ( 14 ) a gear ( 28 ) of at least a second transmission constant (C2) and the first intermediate shaft (12) via a valve disposed between the tooth edges (26, 28) switching element (51) and via the second transmission constant (C2) to the output shaft (20) brought into operative connection is. 8. Gear change transmission according to one of the preceding An claims, characterized, that a gear pair (ZI / II) the lowest and the second lower rigorous gear (I, II) is assigned. 9. gear change transmission according to one of the preceding claims, characterized in that the intermediate shaft ( 12 ) of the first sub-transmission ( 22 ) via the first transmission constant (C1) with a parallel to the input shaft ( 10 ) second countershaft ( 18 ) can be brought into operative connection, which can be brought into operative connection with the output shaft ( 20 ) at least via one of the first partial transmissions ( 22 ) assigned to the gear pair (ZIV / VI), and that the first gear constant (C1) optionally with the first, the second or with both powershift clutches (K1, K2) can be brought into operative connection. 10. Gear change transmission according to claim 9, characterized in that the output shaft ( 20 ) by an engaging and disengaging switching element ( 52 ) to form a direct gear (V) with the intermediate shaft ( 12 ) of the first sub-transmission ( 22 ) can be connected. 11. Gear change transmission according to one of the preceding claims, characterized in that in addition to the first transmission constant (C1) on the first intermediate shaft ( 12 ) at least a second gear constant from the first Ge (C1) different transmission constant (C2) on the second intermediate shaft ( 14 ) and at least one transmission constant (C1, C2) can be brought into operative connection with the output shaft ( 20 ) via both countershafts ( 16 , 18 ). 12. Gear change transmission according to claim 11, characterized, that each gear pair (ZI / II, ZIII / IV, ZIV / VI, ZR) with each Transmission constants (C1, C2) can be brought into operative connection.   13. Gear change transmission according to one of the preceding claims, characterized in that in addition to two transmission constants (C1, C2), three gear pairs (ZI / II, ZIII / IV, ZIV / VI) for six different forward gear ratios (I, II, III, IV , V, VI) and a gear pair (ZR) for at least one reverse gear (R) are arranged and a gear ( 30 ) of the gear pair (ZIV / VI) assigned to the fourth and sixth gear (IV, VI) on a second countershaft ( 18 ), a gear ( 32 ) of the third and fourth gear (III, IV) associated gear pair (ZIII / IV) and a gear ( 34 ) of the first and second gear (Ge, I, II) associated gear pair (ZI / II) is arranged on the first countershaft ( 16 ). 14. Method for switching a gear change transmission according to one of the preceding claims, characterized, that depending on at least one operating parameter, the first the second or both powershift clutches (K1, K2) together be used to start. 15. The method according to claim 14, characterized, that the differential speed at least at a power shift clutch (K1, K2) and the power to be transmitted and depending on the differential speed and the one to be transmitted Power the power shift clutches (K1, K2) individually or ge together used to start.   16. The method according to any one of claims 14 or 15, characterized, that the weight of the motor vehicle including cargo and / or the slope of a route of the motor vehicle detected who the and depending on weight and / or incline the power shift Couplings (K1, K2) individually or together for starting be used. 17. The method according to any one of claims 14 to 16, characterized, that of at least one power shift clutch (K1, K2) setting temperature is detected and depending on the tem perature the power shift clutches (K1, K2) individually and or can be used together for starting. 18. The method according to any one of claims 14 to 17, characterized, that the wear on the power shift clutches (K1, K2) is detected and depending on wear, the powershift clutches (K1, K2) can be used individually or together to start off. 19. The method according to claim 18, characterized, that the power shift clutches (K1, K2) in such a way for starting be set so that both power shift clutches (K1, K2) largely sets the same wear. 20. The method according to claim 19, characterized, that after a certain wear only one of the two Powershift clutches (K1) is used for starting.   21. The method according to any one of claims 14 to 20, characterized, that if one power shift clutch (K1, K2) fails, the other Powershift clutch (K1, K2) is used for starting.