Shifting device and transmission unit

A shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force is disclosed. The shifting device has a first partial transmission and a second partial transmission, which are connected in series for power transmission. The selecting devices of the first partial transmission are designed as selectable free-running clutches and the second partial transmission has a plurality of selectable gear stages. During shifting from a highest stage of the gear stages of the first partial transmission to a lowest stage of the gear stages of the first partial transmission, the free-running clutches of the two gear stages are actuated simultaneously, and a load change between the corresponding free-running clutches allows a shifting operation of the second partial transmission to a higher stage of the gear stages.

BACKGROUND OF THE INVENTION

The invention relates to a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a shaft, on which a plurality of loose wheels is mounted which, with a corresponding plurality of gearwheels, form wheel pairs of at least one partial transmission, wherein the shaft is formed as a hollow shaft and the loose wheels can be connected to the shaft by means of selecting means, wherein the selecting means can be actuated selectively by means of at least one camshaft mounted in the hollow shaft in order to form gear stages of the partial transmission.

The invention furthermore relates to a transmission unit, in particular for a vehicle driven by muscle force, having a shifting device of this kind.

Finally, the invention relates to a method for shifting the abovementioned shifting device.

Such shifting devices and transmission units are used to gear up or gear down driving force, in particular muscle force, and thereby make the vehicle easier to drive.

U.S. Pat. No. 5,924,950 A discloses a bicycle transmission of this kind. This bicycle transmission has an input shaft and a countershaft, wherein a plurality of driving wheels is mounted on the input shaft and a corresponding number of selectable driven wheels is mounted on the countershaft. The selectable gears on the countershaft are selected by means of a plurality of axially movable selector pins and free-running clutches arranged in the countershaft, wherein the countershaft is connected to a pinion as the output member of the bicycle transmission by means of a planetary transmission. The pinion is connected to the sun wheel of the planetary transmission by a clutch, and the annulus of the planetary transmission can be blocked or fixed by means of a Bowden cable. The planetary transmission thereby forms a two-speed transmission, which is connected in series with the seven-speed transmission on the countershaft, thus allowing fourteen gears to be formed by means of the bicycle transmission as a whole. The disadvantage with the system is the axially large form of construction and the relatively small number of fourteen gears that can be formed. It is furthermore disadvantageous that the two partial transmissions must be activated separately and therefore have to be operated with an increased effort. In this context, it is furthermore disadvantageous that the two partial transmissions are not matched to one another and hence that sequential shifting through all the gears and, in particular, simultaneous shifting of both partial transmissions is inconvenient.

DE 10 2008 064 514 A1 discloses another transmission unit for a vehicle driven by muscle force, having an input shaft, an output shaft and a countershaft, wherein a plurality of loose wheels is mounted on the countershaft which, with gearwheels on the input shaft or the output shaft, form wheel pairs of two partial transmissions, and wherein the loose wheels can be connected for conjoint rotation to the countershaft by means of selectable free-running clutches, wherein the free-running clutches can be actuated by means of two separate camshafts. In this case, control of the two camshafts by two separate planetary transmissions is associated with a corresponding space requirement and an additional outlay on control for synchronization of the two partial transmissions.

It is therefore the object of the present invention to provide an improved shifting device and an improved transmission unit for a vehicle driven by muscle force, which unit has a compact form of construction, has improved shifting convenience and can be implemented with low technical effort.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the invention, this object is achieved by a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a shaft, on which a plurality of loose wheels is mounted which form with a corresponding plurality of gearwheels wheel pairs of two partial transmissions, wherein the shaft is designed as a hollow shaft and the loose wheels can be connected to the shaft by means of selecting means, wherein the two partial transmissions are assigned in each case one camshaft which is mounted in the hollow shaft, and the selecting means can be actuated selectively by the camshafts, wherein the camshafts are connected to driving means in order to rotate the camshafts relative to the shaft in order to actuate the selecting means, wherein the camshafts are connected rotationally fixed to one another, and a rotation of the camshafts relative to the shaft brings about an axial movement of one of the camshafts.

According to a second aspect of the invention, this object is achieved by a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a shaft, on which a plurality of loose wheels is mounted which form with a corresponding plurality of gearwheels wheel pairs, wherein the shaft is designed as a hollow shaft and the loose wheels can be connected to the shaft by means of selecting means, wherein the selecting means are assigned a camshaft mounted in the hollow shaft and the selecting means can be actuated selectively by the camshaft, wherein the camshaft is connected to driving means in order to rotate the camshaft relative to the shaft in order to actuate the selecting means, wherein the rotation of the camshaft relative to the shaft causes an axial movement of the camshaft, wherein the camshaft has at least one cam portion which is designed in such a way that the selecting means of different loose wheels can be actuated by the cam portion.

According to a third aspect of the invention, this object is achieved by a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a shaft, on which a plurality of loose wheels is mounted which form with a corresponding plurality of gearwheels wheel pairs of two partial transmissions, wherein the shaft is designed as a hollow shaft and the loose wheels can be connected to the shaft by means of selecting means, wherein the two partial transmissions are assigned in each case one camshaft which is mounted in the hollow shaft, and the selecting means can be actuated selectively by the camshafts, wherein the camshafts are connected to driving means in order to rotate the camshafts relative to the shaft in order to actuate the selecting means, wherein a first of the camshafts is connected to the driving means through a second of the camshafts by means of a drive shaft.

According to a fourth aspect of the invention, the object is achieved by a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a first partial transmission and a second partial transmission, which are connected in series for power transmission, wherein the first partial transmission has a shaft, which is designed as a hollow shaft and on which a plurality of loose wheels is mounted which form with a corresponding plurality of gearwheels wheel pairs of the first partial transmission, wherein the loose wheels can be connected to the shaft by means of selecting means in order to form different gear stages of the first partial transmission, wherein the selecting means can be actuated by a camshaft arranged in the shaft, wherein the selecting means of the first partial transmission are designed as selectable free-running clutches, and wherein the second partial transmission has a plurality of selectable gear stages, wherein the camshaft is designed in such a way that, when shifting from a highest stage of the gear stages of the first partial transmission to a lowest stage of the gear stages of the first partial transmission, the free-running clutches of the two gear stages are actuated at least temporarily simultaneously, and a load change between the corresponding free-running clutches allows a shifting operation of the second partial transmission to a higher stage of the gear stages.

According to a fifth aspect of the invention, the object is achieved by a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a first partial transmission and a second partial transmission, which are connected in series for power transmission, wherein the second partial transmission has a shaft, which is formed as a hollow shaft and on which a plurality of loose wheels is mounted which form with a corresponding plurality of gearwheels wheel pairs of the second partial transmission, wherein the loose wheels can be connected to the shaft by means of selecting means in order to form different gear stages of the second partial transmission, wherein the selecting means can be actuated by means of a camshaft arranged in the shaft, wherein the selecting means of the second partial transmission are designed as selectable free-running clutches, wherein the first partial transmission has a plurality of selectable gear stages, wherein the camshaft is designed in such a way that, when shifting from a higher stage of the gear stages of the second partial transmission to a lower stage of the gear stages of the second partial transmission, the free-running clutches of the two gear stages are actuated at least temporarily simultaneously, and a load change between the corresponding free-running clutches allows a shifting operation of the first partial transmission from a lowest stage of the gear stages of the first partial transmission to a highest stage of the gear stages of the first partial transmission.

According to a sixth aspect of the invention, the abovementioned object is achieved by a shifting device for a transmission unit, in particular for a vehicle which is operated by muscle force, having a shaft, which is formed as a hollow shaft and on which a plurality of loose wheels is mounted which form with a corresponding plurality of gearwheels wheel pairs of different gear stages, wherein the loose wheels can be connected to the shaft by means of selectable free-running clutches, wherein the free-running clutches can be actuated selectively by a camshaft rotatably mounted in the hollow shaft, wherein the camshaft can be rotated in both directions of rotation relative to the shaft by means of driving means in order to actuate the free-running clutches and move them out of engagement with the loose wheels, wherein the free-running clutches have selector pawls mounted rotatably or swivelably on the shaft, and wherein the driving means are designed to rotate the camshaft for a change from a higher gear stage to a lower gear stage in a direction of rotation opposite to the direction of rotation of the selector pawls during disengagement.

According to a seventh aspect of the invention, the above object is achieved by a transmission unit, in particular for a vehicle driven by muscle force, having a continuous shaft, which forms an input shaft of the transmission unit and can be connected at its ends to cranks, an output shaft, which is arranged coaxially with the input shaft, and a countershaft, which has a shifting device of the type described above.

According to an eighth aspect of the invention, the object is achieved by a method for shifting a transmission unit, wherein the gear stages of the transmission unit are engaged and/or changed by means of a shifting device according to the invention.

One advantage of the first aspect of the invention is that the camshafts are interlinked and in that the two partial transmissions can be shifted in a manner dependent one upon the other by the joint rotation of the camshafts, and hence the shifting effort for shifting the two partial transmissions is reduced and the ease of shifting is simultaneously improved. In other words, the shifting device can shift both partial transmissions simply through the joint rotation of the camshafts, thus eliminating separate shifting of the two partial transmissions.

One advantage of the second aspect of the invention is that the cams on the camshaft actuate several of the selecting means and, as a result, there is an increase in the useful axial range of movement, thereby making it possible to achieve a more compact form of construction in the axial direction.

One advantage of the third aspect of the invention is that the two camshafts are rotated or controlled from one axial end, thereby making possible a more compact form of construction in the axial direction and thereby reducing the technical effort involved in controlling the camshafts. In other words, the camshafts do not have to be controlled from two opposite sides but can be rotated or controlled by driving means from one axial end, thereby reducing the outlay for supporting the corresponding shaft.

One advantage of the fourth aspect of the invention is that the two partial transmissions are synchronized and, during a shifting operation in both partial transmissions, i.e. when the first of the partial transmissions is shifted from a highest gear stage to a lowest gear stage and the second partial transmission is simultaneously shifted from a low gear stage to a higher gear stage, precise simultaneous shifting is possible since the second partial transmission is shifted only at the time of the actual load change of the first partial transmission. In other words, it is thereby possible to prevent one of the two partial transmissions from being shifted before the other of the partial transmissions and, as a result, the overall transmission briefly being shifted into a very low gear or a very high gear. Overall, downshifting of the first partial transmission and simultaneous upshifting of the second partial transmission is thereby possible.

One advantage of the fifth aspect of the invention is that the two partial transmissions are synchronized and, during a shifting operation in both partial transmissions, i.e. when the second partial transmission is shifted from a higher gear stage to a low gear stage and the first partial transmission is simultaneously shifted from a lowest gear stage to a highest gear stage, precise simultaneous shifting is possible, thereby making shifting of the transmission unit easier overall.

One advantage of the sixth aspect of the invention is that downshifting under load or under partial load is possible since the corresponding selector pawl can be moved out of engagement with the corresponding loose wheel with a greater force. In the case of downshifting by means of selectable free-running clutches, it is generally necessary greatly to reduce the driving force or briefly to interrupt it completely to ensure that the load on the corresponding selector pawl falls to zero and that it can be retracted by means of a low force before the corresponding selector pawl of the lower gear can be brought into engagement with the loose wheels. Since, according to the fourth aspect of the invention, a significantly higher force must be exerted on the selector pawls in order to retract the selector pawl, the driving force does not have to be interrupted. As a result, it is possible overall to obtain a power shift transmission which can be both upshifted under load and downshifted under load.

In the first aspect of the invention, it is preferred if the camshafts are connected rotationally fixed to one another and axiallly movable by means of a connecting shaft.

As a result, the two camshafts can be connected to one another for conjoint rotation and axial movement by simple means at low cost.

It is furthermore preferred if the axially movable second camshaft has an at least partially circumferential groove having a transverse portion, in which a pin engages, which is connected to the shaft, wherein the transverse portion causes the axial movement at a predefined rotational position of the camshaft.

It is thereby possible reliably to cause the axial movement with low friction at certain rotational positions by technically simple means.

It is furthermore preferred if the axially movable camshaft has at least one cam portion, having an actuating portion for actuating the selecting means by rotation of the camshaft, and an at least partially circumferential sliding portion for maintaining the shift state of the selecting means over a predefined angle of rotation.

It is thereby possible, at a particular rotation, for the selecting means to be actuated by the rotation of the camshaft and to maintain the shift state over a predefined angle of rotation, thereby making it possible to link the shift sequences of the first and second partial transmissions in a logical manner. In other words, it is thereby possible for a shift state in the second partial transmission to be selected and maintained over a number of shifting operations of the first partial transmission.

In this case, it is preferred if the actuating portion and the sliding portion adjoin one another in the direction of rotation.

It is thereby possible for the selected shift states to be maintained over a predefined angle of rotation of the camshafts by technically simple means.

It is preferred here if the selecting means, the cam portion and the obliquely transverse portion are arranged in such a way that the selecting means of different gear stages can be actuated by the cam portion.

It is thereby possible to increase the useful axial range of movement without having to increase the spacing between the selecting means, thereby making it possible overall to achieve a more compact form of construction in the axial direction.

It is furthermore preferred if the sliding portion is designed to completely encircle the camshaft in order to maintain a corresponding shift state over a complete revolution of the camshaft.

It is thereby possible to maintain a shift state of the second partial transmission over a complete shifting sequence of all the gear stages of the first partial transmission, thereby making it possible by simple means to shift through all the gears of the transmission unit.

In the third aspect of the invention, it is preferred if the driving means of both camshafts are arranged at one axial end of the shaft.

It is thereby possible to achieve a form of construction of the shifting device or of the corresponding transmission unit which is compact overall in the radial direction as well.

It is particularly preferred if the driving means have a speed superimposition transmission.

It is thereby possible to achieve a relative rotation between the camshaft and the shaft by technically simple means.

It is particularly preferred here if the driving means have two, in particular three or more, planetary transmissions, which are connected to one another.

It is thereby possible to achieve a compact and technically simple speed superimposition transmission in order to rotate one and, in particular, two camshafts relative to the shaft.

It is preferred here if planet carriers of the planetary transmissions are connected to one another.

It is thereby possible to transmit a speed of rotation to the camshafts via the annuluses of the planetary transmissions with little technical effort.

It is preferred here if the driving means have a transmission stage to transmit the rotation of the shaft to the camshafts, and wherein the driving means have two control stages to separately transmit a relative rotation to the respective camshafts.

It is thereby possible for both camshafts to be rotated synchronously with the shaft by a common transmission stage and for a relative rotation to be transmitted to the camshafts independently of one another, thereby making it possible to implement the driving means in a more compact manner overall and thereby requiring less installation space.

In the fourth and fifth aspect of the invention, it is preferred if the load change allows a movement of the camshaft which initiates the shifting operation in the other of the partial transmissions in each case.

It is thereby possible for a shifting operation of the other partial transmission in each case to be mechanically initiated by technically simple means.

It is preferred here if, in an intermediate state, in which the free-running clutches of the two gear stages of the first partial transmission or of the second partial transmission are actuated simultaneously, the camshaft is preloaded against the corresponding free-running clutch and is released during the load change.

It is thereby possible, by simple means, reliably to determine the actual time of the load change and to transmit it to the second partial transmission. It is thereby possible to achieve simultaneous shifting of both partial transmissions, thereby making it possible to avoid briefly shifting the shifting device to a very much lower gear or to a very much higher gear.

It is preferred here if the second partial transmission is formed by a plurality of loose wheels, which are mounted on the shaft and form with a corresponding plurality of gearwheels wheel pairs of the second partial transmission, wherein the second partial transmission has a camshaft which can be rotated and/or moved axially in the shaft and is designed to perform a gear change in the second partial transmission during the load change and, in particular, to simultaneously actuate free-running clutches of two successive gear stages.

It is thereby possible to achieve a compact form of construction of the shifting device since it is possible to dispense with complex means for linking the shifting operations in the two partial transmissions.

It is preferred here if the free-running clutches have swivelable pawls, which block the rotation of the camshaft in the intermediate state before the load change.

It is thereby possible to implement the shifting device in a compact form of construction and to detect the load change with little technical effort and to transmit it to the second partial transmission.

In the case of all the aspects of the present invention, it is preferred overall if the driving means are designed to rotate the camshaft or camshafts synchronously with the shaft in order to maintain a shift state and to rotate at least one of the camshafts relative to the shaft in order to change a shift state.

It is thereby possible to achieve a simple and compact shifting device.

In the case of all the aspects of the invention, it is furthermore preferred if two successive gear stages can be actuated simultaneously in each case.

It is thereby possible to obtain a power shift transmission, thereby simultaneously preventing neutral pedaling.

It is obvious that the features mentioned above and those which remain to be explained below can be used not only in the respectively indicated combination but also in other combinations or in isolation without exceeding the scope of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

InFIG. 1, a transmission unit is designated in general by10.

FIG. 1shows a side view of a bicycle frame12, which has a transmission housing14, in which the transmission unit10is accommodated. In this illustration, the transmission unit10is indicated only schematically and is designed as a compact unit, which is preferably arranged in a transmission cage (not shown here). In this context, the transmission unit10is described by way of example for use on a two wheeler, wherein the use on other muscle-powered vehicles is also possible. It is obvious that the transmission unit10can also be used for vehicles on which muscle force is used in combination with a driving machine to drive the vehicle.

The transmission unit10and the transmission housing14, together with pedal cranks16and16′, form a multispeed transmission18.

FIG. 2shows a shift diagram for the transmission unit10.

The transmission unit10has an input shaft20and an output shaft22. The input shaft20is designed as a continuous shaft. The output shaft22is designed as a hollow shaft. The input shaft20and the output shaft22are arranged coaxially with one another. The output shaft22is connected rotationally fixed to a chain wheel24, which forms an output member of the transmission unit10.

The transmission unit10has a first partial transmission26and a second partial transmission28. A plurality of driving wheels30,31,32,33,34,35is mounted on the input shaft20. The first partial transmission26has a countershaft36. Driven wheels38,39,40,41,42,43are mounted on the countershaft36. The driven wheels38to43are designed as loose wheels.

The driven wheels38to43can be connected to the countershaft36by means of selecting means (not shown). The driven wheels38to43and the driving wheels30to35form wheel pairs which have different transmission ratios, making it possible to obtain different gear stages through selective connection of the driven wheels38to43to the countershaft36.

The second partial transmission28has an input shaft46. Driving wheels48,49,50are mounted on the input shaft46. The driving wheels48to50are designed as loose wheels. The driving wheels48to50can be connected rotationally fixed to the input shaft46by means of selecting means. The driven wheels52,53,54are mounted on the output shaft22. The driven wheels52to54mesh with the driving wheels48to50.

The intermeshing driven wheels52to54and driving wheels48to50form wheel pairs which have different transmission ratios. The driving wheels48to50can be connected rotationally fixed to the input shaft46by means of selecting means (not shown), thereby forming different selectable gear stages of the second partial transmission28.

The countershaft36of the first partial transmission26is connected rotationally fixed to the input shaft of the second partial transmission28. The countershaft36is preferably formed integrally in one piece with the input shaft46.

The driving wheels30to35are each preferably connected nonpositively by means of a clutch (not shown) and, in particular, frictionally by means of a friction clutch to the input shaft20. The clutch is designed to limit a torque introduced into the transmission unit10. The clutch is designed so that the connection between the input shaft20and the corresponding driving wheel30to35slips if a predefined or adjustable torque is exceeded. By means of a torque limitation feature of this kind, it is possible to reduce the overall size and the weight of the transmission unit since the transmission unit can be designed for a lower maximum torque.

By virtue of the fact that the first partial transmission26is connected to the second partial transmission28, the possible achievable gear stages of the first partial transmission26can be multiplied by the gear stages of the second partial transmission28. Thus, eighteen gears can be obtained by means of the transmission unit10illustrated inFIG. 2.

It is furthermore conceivable that there should be the possibility of connecting the input shaft20rotationally fixed to the output shaft22by means of a clutch (not shown). It would thereby be possible to obtain a further gear as a direct gear.

FIG. 3shows schematically a shift diagram for a shifting device having an axially movable camshaft. InFIG. 3, the shifting device is designated in general by60. In general terms, the shifting device60is used to selectively connect loose wheels (not shown) of two different partial transmissions, said loose wheels being mounted on a shaft62, rotationally fixed to the shaft62by means of selecting means (not shown). The shifting device60has a first camshaft64, which is arranged coaxially in the shaft62and is mounted so as to be rotatable relative to the latter. The shifting device60furthermore has a second camshaft66, which is arranged coaxially in the shaft62and is mounted so as to be rotatable and axially movable relative to the latter. The first camshaft64and the second camshaft66are connected rotationally fixed to one another and axially movable by means of a connecting shaft68.

A speed superimposition transmission70, which is connected both to the shaft62and to camshaft64, is arranged at one axial end of the shaft62. The speed superimposition transmission70is arranged coaxially to the shaft62. The speed superimposition transmission70is formed by a transmission stage72and a control stage74. The control stage74is connected to the shaft62and the transmission stage72is connected to camshaft64. As an alternative, it is also possible for the control stage74to be connected to camshaft64and the transmission stage72to be connected to the shaft62. The transmission stage72is formed by a first planetary transmission72. The control stage74is formed by a second planetary transmission74. The first planetary transmission72has a sun wheel76, which is connected rotationally fixed to camshaft64. The planetary transmission72has planet gears78, which are mounted on a planet carrier80. The planet wheels78mesh with the sun wheel76. The first planetary transmission72has an annulus82, with which the planet wheels78mesh. The annulus82is fixed to a fixed reference point84, preferably a transmission cage or transmission housing (not shown), and connected rotationally fixed thereto.

The second planetary transmission74has a sun wheel86, which is connected rotationally fixed to the shaft62. The second planetary transmission74has planet wheels88, which are mounted on the planet carrier80. The planet wheels84mesh with the sun wheel86. The second planetary transmission74has an annulus90, with which the planet wheels88mesh. The annulus90is connected rotationally fixed to a pulley92, on which a Bowden cable (not shown) can be secured.

The first planetary transmission72and the second planetary transmission74are dimensioned in such a way that, when the annulus90is stationary or fixed, the transmission ratio from the shaft62to camshaft64is precisely1, with the result that the shaft62and camshaft64rotate synchronously in this case. The second planetary transmission74or the control stage74serves to superimpose an additional speed of rotation on the speed of rotation of the shaft62. This additional speed of rotation is transmitted via the annulus90to the planet carrier80. By virtue of the fact that the planet wheels88of the second planetary transmission74and the planet wheels78of the first planetary transmission72are connected to one another by the planet carrier80, a total speed of rotation, being the sum of the speed of rotation of the shaft62and of the rotation of the annulus90, is transmitted to the first planetary transmission72. The first planetary transmission72or the transmitter stage72serves to transmit the total speed of rotation to camshaft64. The annulus90is connected rotationally fixed to the pulley92to enable it to be actuated by means of a Bowden cable (not shown). In this case, the pulley92is rotated through a certain angle of rotation in the direction of rotation of the shaft62or counter to the rotation of the shaft62in order to transmit this rotary motion to camshaft64. As a result, the gears of the transmission unit10can be selected by actuating the Bowden cable. The sun wheel86is preferably designed as part of the shaft62or is integral with the shaft62.

Camshaft66is connected rotationally fixed and axial movement to camshaft64by means of the connecting shaft68. Camshaft66is connected in such a way to the shaft62, via a control pin or the like, that a rotation of camshaft66relative to the shaft62causes axial movement of camshaft66.

As a result, camshafts64and66can selectively actuate selecting means of loose wheels of different partial transmissions, wherein particular shifting sequences of the two partial transmissions can be achieved through the predefined axial movement of camshaft66.

A perspective illustration of the transmission unit10is shown inFIG. 4. The transmission unit10corresponds to the shift diagram shown inFIG. 2, wherein identical elements are designated by the same reference numerals and only the differences are explained here.

The input shaft20has connecting portions94,96at the axial ends thereof in order to connect pedal cranks (not shown) rotationally fixed to the input shaft20. The chain wheel24is mounted on one axial end of the output shaft22(not shown). The chain wheel24is connected to a connecting element (not shown) by means of a central screw94and is thereby connected rotationally fixed to the output shaft22.

The countershaft36is arranged parallel to the input shaft20. The loose wheels38to43and48to50are mounted on the countershaft36, which is formed integrally with the input shaft46of the second partial transmission28. The speed superimposition transmission70is mounted on one axial end of the countershaft36. The loose wheels38to43and48to50can be connected to the countershaft36or selected by means of camshaft64(not shown) in conjunction with the selecting means (not shown), wherein camshaft64can be rotated relative to the countershaft36by means of the speed superimposition transmission70.

A perspective exploded view of the selected device60is illustrated inFIG. 5. Identical elements are provided with the same reference numerals, and only the differences are explained here.

The shaft62has a plurality of recesses98, in which selector pawls100are mounted. The selector pawls100each have an actuating portion101or actuating tab101. The selector pawls100are mounted swivelably or rotatably in the recesses98in order to engage in internal toothing of loose wheels (not shown) and to connect the loose wheels rotationally fixed to the shaft62. The selector pawls100are mounted on the shaft62in such a way that the actuating portions101are arranged in the respective recesses98in a retracted state of the selector pawls100and project into the shaft62in an extended state. The camshafts64,66are mounted rotatably and coaxially in the shaft62. The first camshaft64and the second camshaft66are connected to one another for axial movement and conjoint rotation by the connecting shaft68. For this purpose, the connecting shaft68has a longitudinal groove102, in which a pin104of the second camshaft66engages. The first camshaft64is connected to the shaft62by means of the speed superimposition transmission70in order to achieve a rotation relative to the shaft62. The first camshaft64has a plurality of cams106, which each have an actuating portion108. The cams106and actuating portions108serve to selectively actuate the actuating portions101of the selector pawls100in different rotational positions of camshaft64and thereby to obtain different gear stages of the first partial transmission26.

The selector pawls100are designed in such a way that they swivel outward and connect a corresponding loose wheel of the loose wheels rotationally fixed to the shaft62when no pressure is being exerted by the respective camshaft64,66on the respective actuating portion101of the selector pawls100. For this purpose, the selector pawls100are appropriately spring-loaded. In other words, a selector pawl100is retracted if a sliding portion106,116of the camshafts64,66is arranged underneath the selector pawl100and is extended if an actuating portion108,118is arranged underneath the selector pawl100.

The second camshaft66has a circumferential groove110, in which a pin112engages. The pin112is connected rotationally fixed to the shaft62by means of a bearing ring114. The circumferential groove110in the second camshaft66is designed in such a way that rotation of the second camshaft66relative to the shaft62brings about an axial movement of camshaft66, as explained in greater detail below.

The second camshaft66has two cams116, which each have two actuating portions118and one sliding portion120. The actuating portions118serve to actuate the selector pawls100of the second partial transmission28. The sliding portions120serve to maintain the shift state of the selector pawls100over a predefined angle of rotation of the shaft66, i.e. to hold the selector pawls100in a retracted state.

The sliding portion116of the second camshaft66is designed to be fully encircling, and therefore the corresponding selector pawl100remains retracted over a complete revolution of the camshafts64,66. Fully encircling portions121are formed between the cams116, allowing the respective selector pawl100to extend over a complete revolution of the camshafts64,66and thereby obtaining a corresponding gear stage of the second partial transmission28. The actuating portions118are arranged on the cams116in such a way that they in each case form a connecting ramp between the encircling portions121and the sliding portion120in the direction of rotation of camshaft66. The actuating portions118of a cam116are each preferably arranged offset relative to one another in the circumferential direction and in the axial direction.

An assembly drawing of the shifting device60without the shaft62is shown in perspective inFIG. 6. Identical elements are designated by the same reference numerals, and only the special features are explained here.

The selector pawls100of the first partial transmission26are associated in a fixed manner with the cams106of the first camshaft64. The second camshaft66is arranged in such a way in an axial position relative to the selector pawls100of the second partial transmission28that one of the selector pawls100shown here is retracted due to the sliding portion120. The second cam116is arranged axially adjacent to the second selector pawl100depicted here, with the result that this selector pawl is actuated, i.e. extended, and connects the corresponding loose wheel of the loose wheels rotationally fixed to the shaft62. A further selector pawl100is arranged axially between the first and second selector pawls100, this further selector pawl being concealed by camshaft66in this illustration and being assigned to a second gear stage.

The axially movable second camshaft66is shown in different axial positions inFIGS. 7atodto illustrate the operation. Identical elements are designated by the same reference numerals, and only the differences and special features are explained here.

The pin112engages in the groove110, which has an oblique portion122. Owing to the engagement of the pin112in the groove110, the oblique portion122brings about the axial movement of camshaft66when camshaft66rotates. In the axial position of camshaft66illustrated inFIG. 7a, the actuating portion101of the selector pawl100shown is extended inward, with the result that the selector pawl100is in engagement with internal toothing of the corresponding loose wheel (not shown).

InFIG. 7b, the second camshaft66has been twisted or rotated relative to the illustration inFIG. 7aand has been moved in the axial direction relative to the illustration inFIG. 7aby the pin112engaging in the groove110and by the oblique portion122. By means of such an axial movement and rotation of the second camshaft66, the actuating portion118or ramp118is rotated or moved under the actuating portion101, as a result of which the selector pawl100is retracted accordingly and moved out of engagement with the internal toothing of the associated free pinion.

A further rotational position of the second camshaft66is illustrated inFIG. 7c. In this illustration, the second camshaft66is twisted through about 360° relative to the illustration inFIG. 7c. The second camshaft66has been moved into another axial position by another obliquely extending portion124of the groove110. This has the effect that the actuating portion101is not passed over the ramp118again during a rotation through 360°. By means of the axial movement of the second camshaft66, the actuating portion101is guided over the sliding portion120of the cam116, with the result that the selector pawl110remains retracted over a complete revolution of the second camshaft66.

Another rotational position of the second camshaft66is illustrated in7d. In this rotational position, the second camshaft66has been moved further axially relative to the position inFIG. 7cby another oblique portion126of the groove110. In this position of the second camshaft66, the selector pawl110remains retracted, with the result that the corresponding loose wheel slides on the shaft66.

By means of camshaft66which can be moved axially in this way, the selector pawls100can be actuated or extended selectively and moved out of engagement or retracted in a corresponding manner, and it is possible for the corresponding shift state to be maintained over any desired angle of rotation of the second camshaft66.

The oblique portions122,124,126are arranged in such a way on the circumference of camshaft66that an axial movement takes place if the selector pawls100maintain their shift state. As a result, the frictional forces during shifting can be reduced and an axial movement of camshaft66can take place unhindered.

The selector pawl100illustrated inFIGS. 7atodis correspondingly assigned to one gear stage of the second partial transmission28and is actuated or extended by means of a first complete rotation of 360° of the second camshaft66and retracted or moved out of engagement with the loose wheels by means of the following two revolutions of the second camshaft66. It is thereby possible to shift through the gear stages of the first partial transmission26by means of one complete revolution of the first camshaft64, with the respective gear stage of the second partial transmission28being changed only after one complete revolution. It is thereby possible to shift through all (in this case eighteen) gears of the transmission unit10in a sequence by rotating the two camshafts100.

Two extreme positions of the second camshaft66together with the three associated selector pawls100are illustrated schematically inFIGS. 8aandb. Identical elements are designated by the same reference numerals, and only the special features are explained here.

FIG. 8aillustrates an initial position of the second camshaft66, which corresponds approximately to the first gear of the transmission unit10. In this position, the pin112engages in an axially outermost portion of the groove110. The three selector pawls100are illustrated schematically according to their positions in the respective recesses98in the shaft62. InFIG. 8a, the three selector pawls are designated100′,100″ and100′″ in accordance with their association with the gear stages of the second partial transmission28. The selector pawls100are positioned according to their position in the respective recesses98in the shaft62. In the axial position inFIG. 8a, the cams116are arranged at the axial positions of selector pawls100″,100′″, with the result that the selector pawls100″,100′″ are retracted or moved out of engagement with respective loose wheels by the corresponding sliding portions120. In this position of the second camshaft66, selector pawl100′ is actuated or extended and accordingly connects the shaft62to the corresponding loose wheel. In this position of the second camshaft66, the first gear stage of the second partial transmission28is thus engaged.

Another extreme position of the second camshaft66, corresponding approximately to the 18th gear of the transmission unit10, is illustrated inFIG. 8b. The pin engages in an axially inner portion of the groove110, as a result of which the second camshaft66is arranged in an extreme left-hand position. In this position, selector pawls100′ and100″ are retracted by the sliding portions120, whereas selector pawl100′″ is extended. In this position of the second camshaft66, a third gear stage of the second partial transmission28is engaged.

Accordingly, at least one of the cams116is associated with selector pawls100″,100′″ of different loose wheels of the loose wheels48-50, depending on the axial position of camshaft66, in order to actuate said selector pawls in a corresponding manner or move them out of engagement with the loose wheels.

The axially movable second camshaft66makes it possible, by rotating the first camshaft64, to shift through all the gear stages of the first partial transmission26and, after one complete revolution of the camshafts64,66, to bring about shifting of the second partial transmission.

In an alternative embodiment according to the invention, camshaft66is mounted as a single camshaft in the shaft62, wherein rotation of camshaft66relative to the shaft62brings about the axial movement and actuates the selecting means100accordingly.

In another embodiment, both camshafts64,66are of axially movable design, wherein the axial movement is caused by a rotary movement of the camshafts64,66relative to the shaft62.

A shifting device having two independent camshafts is illustrated and designated in general by130inFIG. 9.

The shifting device130has the shaft62on which a plurality of loose wheels of the two partial transmissions26,28are mounted. Respective camshafts132,134are assigned to the partial transmissions26,28and are designed to actuate the selecting means (not shown here) in order to selectively connect the loose wheels rotationally fixed to the shaft62and thus obtain different gear stages of the transmission unit10. Arranged at one axial end of the shaft62is a speed superimposition transmission136, which is connected both to the shaft62and to each of the camshafts132,134. The speed superimposition transmission136is arranged coaxially with the shaft62. The speed superimposition transmission136has a transmission stage138and two control stages140,142. The transmission stage138is connected to the shaft62and the control stages140,142are each connected to one of the camshafts132,134. The transmission stage138is formed by a first planetary transmission138. The control stages140,142are each formed by a planetary transmission140,142. The planetary transmissions138,140,142are of identical design to the corresponding planetary transmissions inFIG. 3. The planet wheels of the individual planetary transmissions138,140,142are connected to one another by means of a common planet carrier144. The planetary transmission of the transmission stage138is connected to the shaft62and to a transmission housing (not shown). The control stages140,142each have a pulley146,148, these being connected to the respective annuluses.

By virtue of the connection of the planet wheels of the planetary transmissions138,140,142, the two camshafts132,134are rotated synchronously with the shaft62when the pulleys146,148are stationary. If one of the pulleys146,148is rotated, the rotation or the corresponding angle of twist is transmitted to the respective camshaft132or134. As a result, camshafts132,134can be rotated independently of one another relative to the shaft62, and the gear stages of the corresponding partial transmissions26,28can be selected independently of one another. Moreover, an axially compact form of construction is thereby possible since the planetary transmission138,140,142is arranged at only one axial end.

The shifting device130has at least two of the control stages140,142. In a special embodiment, the shifting device130has three or more of the control stages140,142in order to actuate separate selecting means.

Different loose wheels of the first and second partial transmissions26,28, together with the shifting device60fromFIG. 3, are illustrated schematically in an axial direction of view inFIGS. 10atodin order to elucidate the synchronization according to the invention of the two partial transmissions26,28.

Fundamentally, there is the problem, in the case of partial transmissions connected mechanically in series, that, when shifting via the highest gear of the first partial transmission26, the first partial transmission is shifted to the lowest gear stage and, at the same time, a gear stage in the second partial transmission28is shifted to a higher gear stage. If the actual load changes or shifting times of the two partial transmissions26,28do not take place simultaneously, the gear stage of the overall transmission unit is shifted briefly either to a very low gear or to a very high gear.

In the present example, the first partial transmission26has six gear stages and a second partial transmission28has three gear stages. If a shift is made from the sixth gear of the transmission unit10to the seventh gear, a shift is made from the sixth gear stage to the first gear stage in the first partial transmission26and, at the same time, from the first gear stage to the second gear stage in the second partial transmission28. Similarly, a shift is made in the second partial transmission28from the second to the third gear stage when shifting from 12th to 13th gear. If the two partial transmissions26,28do not shift fully simultaneously, a shift is made briefly either from sixth (or twelfth) gear to first (or seventh) gear, if the first partial gear26is shifted first, or from sixth (or twelfth) gear to twelfth (or eighteenth) gear, if the second partial transmission28is shifted first.

InFIGS. 10atod, the loose wheels38and43of the sixth and first gear stages of the first partial transmission26and the loose wheels48and49of the first and second gear stages of the second partial transmission28are shown in the axial direction of view at four points in time during a shifting operation from sixth to seventh gear of the transmission unit10.

The loose wheels each have internal toothing149, in which one of the free-running clutch pawls100engages in order to connect the loose wheels rotationally fixed to the shaft62. If one of the actuating portions108,118of the camshafts64,66is arranged underneath one of the actuating portions101of the selector pawls100, the respective selector pawl100swivels out and engages in the internal toothing149of the loose wheels in order to connect them rotationally fixed to the shaft62. If a sliding portion106,120of the camshafts64,66is arranged underneath the actuating portions101, the respective selector pawl100is retracted and the corresponding loose wheel slides on the shaft62. InFIG. 10a, the sixth gear of the transmission unit is engaged. In this case, the sixth gear stage of the first partial transmission26is engaged and the first gear stage of the second partial transmission28is engaged. In this case, the loose wheel38associated with the sixth gear stage is connected rotationally fixed to the shaft62, and the loose wheel43associated to the first gear stage slides on the shaft62. In the second partial transmission28, the loose wheel48associated with the first gear stage is connected rotationally fixed to the shaft62, and the loose wheel49associated with the second gear stage slides on the shaft62.

In order to shift from the gear of the transmission unit10which has been engaged in this way to seventh gear, the camshafts64,66, which are connected for conjoint rotation, are rotated in the direction of arrow150until an “intermediate state” is achieved, which is shown inFIG. 10b.

In the intermediate state, both selector pawls of the first gear stage and of the sixth gear stage of the first partial transmission26are actuated or extended. In this state, the sixth gear stage is engaged, as indicated by a cross152. In this intermediate state, the sixth gear stage remains engaged since, in this case, loose wheel38runs faster than loose wheel43, with the result that loose wheel43slides across the selector pawl100. The first camshaft64is rotated in the direction of the arrow150until it rests on the actuating portion101of the selector pawl of the sixth gear stage and exerts a corresponding force on the selector pawl100. In this rotational position of the camshafts64,66, the selector pawl100of the first gear stage of the second partial transmission28is actuated or extended and the selector pawl100of the second gear stage of the second partial transmission28is retracted. If a driving forcer of the transmission unit10is reduced and the force exerted by camshaft64on the actuating portion101is sufficient to move the selector pawl100out of engagement with loose wheel38, said selector pawl100retracts and, at the same time, loose wheel43is connected rotationally fixed to the shaft62, and the first gear stage of the first partial transmission26is thereby engaged. By virtue of the fact that camshaft64is preloaded relative to the selector pawl100of loose wheel38, a further rotation of the camshaft64is caused during the retraction of the selector pawl100, thus canceling the intermediate state inFIG. 10b, as shown inFIG. 10c. In this state, the first gear stage is engaged in the first partial transmission, as indicated by the cross152. At the same time, camshaft66together with camshaft64is rotated further by an angle of rotation of about 30°, with the result that the selector pawl100of loose wheel49is extended. Since the higher, second gear stage forms the faster running gear stage in the second partial transmission, the second gear stage is engaged immediately with the extension of the selector pawl100, as indicated by a cross154. At this time, therefore, the first gear stage is engaged in the first partial transmission26and the second gear stage is engaged in the second partial transmission28, with the result that the seventh gear of the transmission unit10is engaged.

By virtue of the fact that the selector pawl100of loose wheel38initially prevents the camshafts from rotating further and, when the camshafts64,66rotate further, the selector pawl100of loose wheel49connects loose wheel49immediately rotationally fixed to the shaft62due to the higher speed of rotation and, at the same time, the selector pawl100of loose wheel43connects the latter rotationally fixed to the shaft62, there is simultaneous shifting in both partial transmissions26,28. In other words, the load change in the first partial transmission allows both camshafts64,66to rotate further, causing an immediate shifting of the gear stages of the second partial transmission. As a result, the two partial transmissions26,28are fully synchronized during the shift from the sixth to the seventh gear of the transmission unit10.

In this shift state fromFIG. 10c, the second partial transmission28is in an intermediate state in which both associated selector pawls are extended. Since loose wheel49is the fast running wheel, loose wheel48slides over the shaft62.

If a shift is being made from seventh to eighth gear, a shift is then initially made to an intermediate state of the first partial transmission by actuating the selector pawls100of the first and second gear stages, thereby retracting the selector pawl100of loose wheel48of the first gear stage of the second partial transmission28.

During a shifting operation from the seventh gear of the transmission unit10to the sixth gear, the first partial transmission26is consequently shifted from the first gear stage to the sixth gear stage, and the second partial transmission is simultaneously shifted from the second gear stage to the first gear stage. Conversely, for upshifting, the second partial transmission28is in this case initially shifted to an intermediate state by actuating or extending both corresponding selector pawls100. Camshaft66is correspondingly preloaded against one of the selector pawls100and is released during a load change, with the result that camshaft66rotates further and causes an intermediate state in the first partial transmission26. In this intermediate state, shifting or the load change is carried out immediately by the selectable free-running clutches100and the rotational speeds of the corresponding loose wheels38,43. As a result, it is likewise possible to perform shifting synchronously and simultaneously in both partial transmissions26,28when downshifting the transmission unit10.

It is obvious that such synchronization of the two partial transmissions26,28can be applied both to the shifting device60inFIG. 3and to other shifting devices, such as camshafts which are capable only of rotation or camshafts which are capable only of axial movement. Moreover, the second partial transmission can also be designed as a shiftable planetary transmission or the like.

The operation of the selector pawl100is explained in greater detail inFIGS. 11aandb. The selector pawl100is mounted in one of the recesses98in such a way as to be rotatable about an axis160. The selector pawl100engages in internal toothing162of a loose wheel164in order to connect the loose wheel164rotationally fixed to the shaft62. Camshaft62has the actuating portion108, with the result that the selector pawl100retracts in a retraction rotation about the axis160, as indicated at165. Camshaft64is rotated in the direction of an arrow166counter to the extension direction165of the selector pawl100, with the result that actuating portion108touches actuating portion101at a first contact point168. By means of the rotation of camshaft64, a torque is exerted on the selector pawl100, retracting the selector pawl100. The magnitude of the torque corresponds to the force which is exerted on the contact point168and to a lever arm170formed by the distance170between the contact point168and the axis of rotation160.

InFIG. 11b, a direction of rotation of camshaft64in the opposite direction is shown and is indicated by an arrow172. This direction of rotation172is identical to the extension direction165of the selector pawl100. In this direction of rotation, actuating portion106touches actuating portion101at a second contact point174. The rotation of camshaft64exerts a torque on the selector pawl100corresponding to the force which is exerted on the contact point174and to a second lever arm176formed by a distance176between the second contact point and the axis of rotation160.

The first lever arm170is consequently greater than the second lever arm176, so that, during a rotation of camshaft64counter to a retraction direction165of the selector pawl100, a larger torque is exerted on the selector pawl100.

During shifting from a higher gear stage to a lower gear stage, the selector pawl100remains extended owing to the transmitted load and owing to the shift from a high speed to a low speed, and therefore shifting is generally not possible without a load reduction. By virtue of the fact that a larger torque is exerted on the selector pawl100in the case of a direction of rotation of camshaft64counter to the retraction direction165, this rotation allows downshifting under load and under a higher load than in the case of the opposite direction of rotation of camshaft64, as explained in greater detail inFIGS. 12atof.

InFIGS. 12atof, the loose wheels42,43of the first gear and of the second gear are illustrated schematically and in an axial direction of view in order to illustrate shifting from the second gear to the first gear. InFIGS. 12aandb, the second gear is engaged, wherein the selector pawl100of the second gear is extended and the selector pawl100of the first gear is retracted. By turning camshaft64further in arrow direction166, an intermediate state is achieved, in which the selector pawls of the two gears1and2are actuated. In this intermediate state, the faster running loose wheel42, the loose wheel42of the second gear, is connected rotationally fixed to the shaft62, while the loose wheel43of the first gear slides on the shaft62. In the state inFIG. 12d, a force is exerted on the selector pawl100in order to retract the selector pawl100, as already illustrated inFIG. 11a. As a result, retraction of the selector pawl100is brought about, as illustrated inFIG. 12f. As a result, the selector pawl100of the first gear engages in the internal toothing162of loose wheel42, and therefore the first gear is engaged.

By means of the rotation of camshaft64during shifting from a higher to a lower gear stage counter to the retraction direction165of the selector pawls100, it is thus possible to exert a larger torque on the selector pawl100, thereby enabling the selector pawl100of the respectively higher gear to be moved out of engagement with the internal toothing162, even under load or partial load. As a result, it is possible to downshift even under load.