DD245935B5 - power shift - Google Patents

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to transmissions for vehicles driven by combustion engines whose operating conditions require the transition from one gear to the other without interruption of traction. These are in particular transmissions for vehicles which apply large tractive forces at relatively low kinetic energy, eg. As heavy tractors, earthmoving equipment, dump trucks, motor graders, loaders and other vehicles that need to overcome large slopes or move in unpaved terrain.

Characteristic of the known technical solutions

In construction machines such as loaders, graders, skrapers, heavy-duty vehicles, car-mounted cranes, forklifts, all-terrain vehicles and buses, power shift gearboxes of various designs are used.

Thus, such transmissions are used in which a hydrodynamic torque converter, usually designed as a Trilok converter, is connected to downstream non-positively connected step gears. These highly loaded by the turbine torque of the torque converter and in particular in the other reduction stages clutches build accordingly large. Also, the friction work is great when switching. In these transmissions, in addition to the unavoidable power losses in the torque converter additional losses caused by the drag torque of the open, not lying in the power flow couplings.

To increase the fuel economy, it is customary to bridge the hydrodynamic converter with a clutch in the upper speed range of the gear ratios or to use the converter only in the 1st or 1st and 2nd gear as traction and off in the higher gears by bridging. These measures are known from connected by multi-plate clutches transmissions (DE-PS 1131107).

In other known transmissions [ATZ 71 (1969) 1], in addition to the drag moments are avoided by the gears are switched by jaw clutches. For this purpose, however, it is necessary to arrange a separating clutch between the converter and the step transmission with the disadvantage of the complete interruption of traction during gear change.

In powershift transmissions with hydrodynamic torque converters with internal power split (DE-OS 1813814), the number of shift stages in the power shift transmission is reduced. The torque converter mentioned and also the required planetary gear are relatively expensive. The converter losses are present in a considerable output speed range. Furthermore, powershift transmissions are known without hydrodynamic torque converter, in which two parallel-connected non-positive clutches are arranged in series with form-locking step clutches, which are non-switchable in each lying in the power flow drive train (VDI Report No. 466,1983). Although the non-positive clutches of these transmissions are arranged at the transmission input, they or at least one of them must be designed with respect to the mechanical and thermal loads for the particularly difficult starting process.

Allen mentioned transmission types has the disadvantage that for switching the gears each one or more positive clutches open and one or more positive clutches are close, the interaction must be coordinated in a timely manner. If the loss of traction during switching is to be minimized, complicated automatic circuits are required, especially in the case of the former and the mechanical powershift transmission.

Object of the invention

The object of the invention is the improvement of powershift transmissions by reducing the power losses and the wear of the power transmitting switching elements, ensuring low output side torque losses during switching regardless of the shift duration, the said effects are achieved with little automation effort and also obtained in the non-automatic gear change substantially stay.

Explanation of the essence of the invention

The object of the invention is to provide a power shift transmission with a simple structure, which allows the switching of the tap-change without interruption of traction by a meaningful combination of positive and non-positive clutches.

The essence of the invention is that in a switchable by positive clutches step transmission a purely mechanical and a hydrodynamic-mechanical power transmission branch are arranged in parallel, one of which is turned on in gears and the other takes over the power transfer during the necessary load-free operation of form-fitting couplings.

According to the invention, the hydrodynamic torque converter (referred to in the text as "converter") is arranged in parallel connection to two adjacent gear stages in each case by means of a primary-side force-acting clutch and a secondary-side overrunning clutch or only a secondary-side force-acting coupling.

The operation of the converter with high efficiency is inventively achieved by a respective two adjacent grades associated adaptation of the converter turbine to the mechanical transmission by means of toothed drives, which are load-free switchable in more than one gear gradation (that is, more than two courses).

In the transmission according to the invention with mechanical power transmission with engaged gear stages, the switching process takes place in three successive phases:

1st phase: To the mechanical lower gear, the converter is connected in parallel. He takes over completely or partially

the power transmission.

2nd phase: The mechanical transmission part is disconnected from the engine. The converter alone takes over the power transmission.

In the unloaded mechanical part of the next higher gear by pressing positive clutches, z. B. jaw clutches, inserted in the usual way.

3rd phase: To the converter, the mechanical higher gear is connected in parallel. The switching process is through the

Disconnecting the converter from the engine immediately after completion of the 3rd phase ended.

For the downshift, the same applies analogously.

Each phase can be maintained for a longer time in addition to the fast connection of the multi-plate clutches. The smallest torque occurs at the transmission output in the 3rd phase and loves about 10% under the torque after completion of the switching operation.

Generally, during upshifting, a gradual defined lowering of the torque with smooth transitions occurs from the higher torque of the lower gear to the lower torque of the higher gear. By a correspondingly matched converter recording power and a gradual lowering of the engine speed (and thus no sudden delay when switching the mechanical part in the higher gear) can be achieved.

In the transmission according to the invention with hydrodynamic-mechanical power transmission with gears engaged, the switching process also takes place in three successive phases:

I.Phase: At the bottom, when the hydrodynamic torque converter is switched on, the mechanical power transmission is switched on in parallel.

With appropriate kinematic design of the corresponding gear pairs and the correct choice of the switching point, the connection takes place without load.

Phase 2: The torque converter is decoupled and thus the hydrodynamic power transmission between engine

and stepped gearbox interrupted. The mechanical transmission part alone takes over the power transmission. In the unloaded, the converter downstream change gear, the next higher gear is engaged by pressing positive clutches in the usual way.

3rd phase: For mechanical power transmission, the torque converter is connected in parallel. The power transmission

takes over the converter driven gearbox in the higher gear.

The switching operation is completed by disconnecting the mechanical branch from the engine immediately after completion of the third phase.

For the downshift, the same applies analogously.

Even with this transmission design according to the invention, each phase except the fast connection of the multi-plate clutches can be maintained for a long time.

At the transmission output the torque remains a priori when switching.

According to the invention, two non-positive clutches (hereinafter referred to as "multi-plate clutches") are provided: one for the connection of the converter with the engine or with the mechanical transmission part and the other for the connection of the mechanical transmission part with the engine.

The arrangement of 2 multi-plate clutches between the engine and transmission is known in purely mechanical powershift transmissions.

A difference of the invention to these transmissions is that only one of the two multi-plate clutches has the same task as in the said transmissions, namely to connect the engine with the mechanical transmission part. Their switching time results as in the known solutions exclusively from the permissible dynamic loads during deceleration of the engine. In this case, in the transmission according to the invention has the advantage that said coupling is partly or completely relieved when switched by the converter, so that a reduced or no friction work arises.

The second multi-plate clutch is loaded exclusively by the primary side of the converter. The occurring maximum power loss is also independent of the gear ratio and is less than 20% of the rated power. Also, this coupling can be switched on quickly, so that minimal friction work arises.

The arrangement of a multi-disc clutch between the engine and mechanical transmission and between the converter output (secondary side) and synchronized change gear is known. The difference of the invention to these transmissions is that both multi-plate clutches are not connected in series with respect to the mechanical transmission part, but in parallel.

In addition to the reduced load on the two multi-plate clutches follows from their arrangement according to the invention another advantage: the multi-plate clutches are never operated simultaneously, so that a timely adjustment of their torque increase or -abfalls is not required.

The converter of the transmission according to the invention with predominantly mechanical power transmission is in addition to its property as bridging converter advantageously - and as known per se also used as start-up converter, so that none of the multi-plate clutches is used as a slip clutch in the particularly stressful starting range.

embodiment

The invention will be explained in more detail below using an exemplary embodiment. In the accompanying drawing show:

1 shows the scheme of a two-speed transmission,

Fig. 2a and 2b: the torque curve at the transmission input side or - output side when changing gear, Figure 3: the scheme of a four-speed transmission with three powershift gears, Figure 4: the scheme of a five-speed transmission with primary-side converter clutch and load switching capability in all

Change gear, Fig. 5: the Scheme of a five-speed transmission with secondary-side converter clutch and load shifting capability in all gear changes.

In Fig. 1, a power shift transmission is shown in the following structure: a drive shaft 1 is connected via a multi-plate clutch 2 with a converter 3 and a multi-plate clutch 4 with a stepped transmission via a gear pair. The step transmission consists of pairs of gears I and Il on a countershaft 6, which can be connected to this alternatively by means of a dog clutch 7. The output gears are firmly seated on an output shaft 8. The turbine wheel T of the converter 3 is connected by an overrunning clutch 9 to the output shaft 8.

The kinematics of the reverse gear or the reverse gears should be designed in a conventional manner and is not shown.

The mode of action should first be explained using the example of the two-speed transmission (the starting phase is not considered as a separate gear in this example) according to FIG. 1. When the engine starts, the multi-plate clutch 2 is open. The multi-plate clutch 4 may be closed or opened. By a filling pump, not shown, which expediently also the pressure oil for actuating the multi-plate clutches 2; 4, the converter 3 is filled.

The dog clutch 7 is in the neutral center position. There is no power transmission. To start the multi-plate clutch 2 is closed quickly and the multi-plate clutch 4 is opened. The converter 3 transmits the power via the overrunning clutch 9 to the output shaft 8. The required starting torque and accordingly the starting tractive force is metered via the engine speed. After opening the multi-plate clutch 4, the jaw clutch 7 is engaged in the position of the 1st gear when stationary or during startup. At the conclusion of the start-up phase, first, the multi-plate clutch 4th

closed. Thus, via the gear pair 5, the countershaft 6, the gear pair I, the purely mechanical power transmission to the output shaft 8 is produced. The power share over this branch increases as it decreases across the transducer 3. When connecting the multi-plate clutch 4, the engine speed is reduced according to the ratio of the gear I. Accordingly, the power consumption and transmission of the converter 3 also decreases. After switching on the multi-plate clutch 4, the multi-plate clutch 2 is opened. The switching point of the transition from pure converter operation in the exclusively mechanical power transmission can be done by the driver or an unillustrated automatic control system. Switching should be initiated at that output speed at which the output torque at converter power transfer is equal to the output torque at mechanical power transfer. Further acceleration takes place in 1st gear up to the maximum speed of this gear.

The operations when switching from a low to a higher gear show Fig.2aund2b. The indices for the torque M and the rotational speed η correspond to the numbers of the associated components in FIG. 1. The higher engine torque immediately after the changeover is due to the elasticity of the engine.

To switch to 2nd gear, the multi-plate clutch 2 is activated. The converter 3 takes over at fully closed multi-plate clutch 4 completely the power transmission with high efficiency (usually over 80%). This is achieved by a suitable choice of the translations of the gear pairs 5 and I. When the multi-plate clutch 4 is closed, the engine speed is still unchanged. Now the multi-plate clutch 4 is opened. Depending on the converter power consumption, the engine speed remains unchanged or drops by a defined amount. When the multi-plate clutch 4 is open, the gear II is engaged with the dog clutch 7 and then the multi-plate clutch 4 is closed again. The engine speed decreases according to the ratio of the gear stage II. Accordingly, the power transmission across the converter 3 decreases. The multi-plate clutch 4 is relieved when connected by the converter 3. After the engine speed has dropped, the multi-plate clutch 2 is opened, so that the power transmission takes place again exclusively by mechanical means. In this operating state, the turbine wheel T of the converter 3 is separated from the output shaft 8 by the overrunning clutch 9

 The switch-back procedure is analogous.

In Figure 3, a power shift transmission is shown, in addition to the elements described in Fig. 1, the gear pairs III and IV, a jaw clutch associated therewith 10, a second countershaft 11 with a matching ratio 12 and a dog clutch 13. The transmission is built in its mechanical power branch like a conventional four-speed gearbox. However, it has the tensile force properties of a five-speed transmission due to the converter effect in the starting range. The starting process as well as the mechanical gears I to III are load-switchable in the sense of the invention as described above. The transition from the gear III to the gear IV (overdrive) is designed with the advantage of a simple structure without the use of the converter 3. In this area, the dynamics of the gear change is cheaper than in the lower gears, so that in certain applications, a simple switch is possible.

For powershift transmissions with more than two gears, the secondary-side adjustment of the converter 3 must be made to two adjacent gears by separate translations. In the embodiment of Figure 3, this is provided by the arrangement of a second countershaft 11, the gears of which are engaged with the gears of the gears Il and IN of the output shaft 8 and which is connected by means of the adjustment ratio 12 with the turbine T of the converter 3. Switching takes place as described above. As an additional switching function, the converter gear ratio associated with the intended gear change to the output shaft 8 is inserted before closing the multi-plate clutch 2 with the dog clutch 13. The translation of the engaged pinion II 'corresponds to the switching from the starting stage in the 1st mechanical gear and from the 1st to the 2nd mechanical gear and back. The translation of the engaged pinion 111 * corresponds to the switching from the 2nd to the 3rd mechanical gear and back. Fig. 4 shows in a further embodiment of the invention, a five-speed powershift transmission with increased starting effect of the converter (and thus reduced fuel consumption in this area) and load shift capability in all gear changes. It differs from the embodiment according to Figure 3 in that the second countershaft 11 in addition gears for coupling to the gears of the I. and IV. Ganges the output shaft 8 and instead of the dog clutch 13 jaw clutches 14 and 15 contains. The claw clutch 14 is, as already described in Figure 3, engaged to switch to the second mechanical gear in the pinion ΙΓ. In the toothed drive Γ, the dog clutch 14 is engaged only in the starting range in hydrodynamic power transmission (before closing the multi-plate clutch 2). As a result, in this area, in contrast to the embodiment according to FIG. 3, the greater reduction of the I. gear is used and a pronounced starting transient gear is realized, while in the embodiment according to FIG. 3 the favorable gear reduction of the second gear is used ( whereby even in comparison to the purely mechanical power transmission, a torque increase in the order of a step increment is achieved). The claw clutch 15 is engaged in the pinion gear IV * prior to switching from gear ll to gear III into the gear train III * and before switching from gear III to gear IV.

Fig. 5 shows another embodiment of the inventive concept, also shown using the example of a five-speed transmission. In this embodiment, the impeller P of the converter 3 is in operation not detachably connected to the drive shaft 1. The turbine wheel T can be coupled to the input of the mechanical transmission part by a multi-plate clutch 16. The stator L is supported in a known manner via a freewheel 17 on the transmission housing. In contrast to the embodiments according to FIGS. 1, 3 and 4, in the embodiment according to FIG. 5, the converter 3 is switched on and off during the starting and switching of the gears by the secondary-side multi-disc clutch 16. The functional sequence is the same as described above. Instead of the multi-plate clutch 2 in Figures 1,3,4, the multi-plate clutch 16 is actuated in this embodiment.

If it turns out in the attempt of upshifting that the drag torque is in its magnitude between the higher low gear torque and the higher gearshift due to the incremental lower gear, stable operation other than returning to the low gear is also without substantial delay remaining in the second switching phase, d. H. with exclusive power transmission via the converter 3 with closed multi-plate clutch 2 and open multi-plate clutch 4, possible.

Using the example of FIG. 5, the second basic mode of operation of the power shift transmission according to the invention will be shown. It is switched on gear ratios of the converter 3. When changing gear, the power transmission is maintained by the temporarily switched mechanical power transmission. This type of application is for particularly difficult driving conditions in which the full engine power over the entire driving range to be exploited and traction levels in the transition from one gear to the next are not allowed appropriate. The functional sequence is as follows: With the engine running and the converter 3 full, the jaw clutches (7; 10; 14; 15) are in the neutral center position; the clutch 4 is open, the clutch 16 is closed or opened. To start the clutch 16 is opened, the dog clutch 14 connected to the pinion Γ and the multi-plate clutch 16 is closed again. The power transmission takes place in first gear via the converter 3, the multi-plate clutch 16, the adjustment ratio 12 on the countershaft 11 and from there via the pinion Γ to the output shaft 8. With increasing vehicle speed, the torque decreases at the output according to the converter characteristic. Upon reaching the switching speed, which corresponds to the torque intersection point of two adjacent gears, the dog clutch 7 is connected to the pinion I and the multi-plate clutch 4 is closed and thus coupled to the purely mechanical power transmission, which is still completely unloaded at still closed multi-plate clutch 16. During the subsequent opening of the multi-plate clutch 16, the mechanical power transmission via the multi-plate clutch 4, the gear pair 5, the countershaft 6, the pinion I to the output shaft 8 is automatically effective. The output torque is maintained in full. The unloaded dog clutch 14 is pushed out of the toothed drive Γ into the toothed drive II 'and then, with the multi-disc clutch 4 still closed, the multi-disc clutch 16 is closed again. The converter 3 takes over the power transmission again. The switching process is completed by releasing the multi-plate clutch 4. The upshift to the next gear is analog. The switchback is in reverse order. Thus, via the pinions Γ to IV, the power transmission with upstream converter in four gears, in the change over the gear stages I to III, the power transmission is temporarily maintained purely mechanically. The fifth gear is a mechanical overdrive with a bridged converter. The power transmission takes place via the multi-plate clutch 4, the gear pair 5, the countershaft 6 and the gear IV to the output shaft 8. In this way it is ensured that the maximum speed is achieved both at full load and at partial load with high efficiency. In the transition from the fourth (converter) gear in the fifth gear, the multi-plate clutch 4 is closed. The multi-plate clutch 16 can remain closed.

Claims (11)

claims: 1. powershift transmission, consisting of two non-positively acting clutches, an output shaft with gears, one or two countershafts with gears and positively acting clutches, a hydrodynamic torque converter, an overrunning clutch and controls, characterized in that parallel to a designed as a purely mechanical power transmission transmission part one or more gear stages (I to IV) is arranged as a different hydrodynamic-mechanical power transmission gear part with one or more gear ratios (Γ to IV) and upstream hydrodynamic torque converter (3), a transmission part as a change gear with positively acting clutches (7; ) and the other gear part as a change gear with positively acting clutches (13; 14; 15) or fixed gear gradation is formed and between the purely mechanical transmission part and the drive shaft (1) and before or after the hydrodyna mix torque converter (3) both alternatively and jointly switchable non-positively acting clutches (2; 14; 16) are arranged. 2. Powershift transmission according to claim 1, characterized in that the turbine wheel (T) of the hydrodynamic torque converter (3) by an overrunning clutch (9) is connected to the output side of the transmission, wherein the overrunning clutch (9) is arranged so that a torque transmission only from the turbine wheel (T) to the output side is possible. 3. Powershift transmission according to claim 1, characterized in that the hydrodynamic torque converter (3) by the gears of the output shaft (8) of the transmission and / or an adjustment ratio (12) in Drehzahlverhältnisseines turbine wheel (T) to its impeller (P) is tuned in that it is operated in the areas of high efficiency when the adjacent gear stages are switched on. 4. Powershift transmission according to claim 1, characterized in that the power consumption of the hydrodynamic torque converter (3) for relieving the arranged between the engine and mechanical transmission part frictionally switchable clutch (4) exceeds the power of the engine for the vehicle drive at rated engine speed. 5. Powershift transmission according to claim 1 and 3, characterized in that for adjusting the rotational speed of the turbine wheel (T) of the hydrodynamic torque converter (3) to the rotational speed of the output shaft (8) in transmissions with more than two gear ratios between the turbine wheel (T) of the hydrodynamic torque converter (3) and the output shaft (8) toothed drives (Γ to IV) are provided different translation, the load-free alternatively by means of positively acting clutches (13 and 15) are switched on in the power flow. 6. Powershift transmission according to claim 1,3 and 5, characterized in that the form-fitting acting clutches (2; 4; 16) of the mechanical transmission part and the transmission part with upstream hydrodynamic torque converter (3) are equipped with synchronizers. 7. Powershift transmission according to claim 1, characterized in that its actuating means or control means are constructed so that only one of the clutches of the transmission is actuated. 8. Powershift transmission according to claim 1, characterized in that the non-positively acting clutch (4) of the mechanical transmission part as predominantly closed (opening during the switching operation) and the non-positively acting clutch (2; 16) of the transmission part with upstream hydrodynamic torque converter (3) as predominantly open (closing during the switching process) coupling is formed. 9. Powershift transmission according to claim 1, characterized in that the non-positively acting clutch (4) of the mechanical transmission part as predominantly open (closing during the switching process) and the non-positively acting clutch (2; 16) of the transmission part with upstream hydrodynamic torque converter (3) as predominantly closed (opening when changing gear) coupling is formed. 10. Powershift transmission according to claim 1, characterized in that in the power branch with hydrodynamic torque converter (3) between the drive shaft (1) and the impeller of the torque converter (3), a gear ratio can be arranged. 11. Powershift transmission according to claim 1, characterized in that one or more gear ratios for the mechanical power transmission and one or more gear ratios for the hydrodynamic-mechanical power transmission are provided with inlaid gears.