The present invention relates to a dual clutch transmission architecture, in particular a dual clutch transmission architecture for an off road vehicle such as an agricultural vehicle and to a related method for controlling the gear shifting of such dual clutch transmission.
Transmissions for off road vehicles such as agricultural vehicles offer different configuration, for instance:
An important request that must be satisfied in modern mechanical transmission for agricultural vehicles is to have high efficiency across the full ground speed range, in order to improve the vehicle fuel consumption. In this respect a large use of wet clutches to build the semi-powershift or the full-powershift transmissions, generates more power losses inside the transmission when compared to the use of synchronizers and dog-clutches and, as consequence, a penalty of efficiency as consequence.
For this reason, in the art, the dual-clutch transmission, DCT, architecture is considered the most valuable layout for powershift transmissions in order to satisfy all the previous demands:
Because of these advantages, recently DCT architecture has been applied in the field of the transmissions for agricultural vehicles. An example of such DCT architecture is disclosed in patent document WO2019091953 A1.
However such known architectures used big wet clutches that dissipate a considerable amount of energy, in particular for allowing shift between range gears.
Moreover, during shifting between gear ratio or range gear ratio, the inertia of the carried transmission elements is considerable. Therefore resistant torque is high and the fuel consumption is not neglectable during shifting.
In conclusion, the need is felt to improve existing DCT architecture for agricultural vehicle in order to improve their performances in all its working speed ranges and to improve the comfort during all gears shifting.
Aim of the present invention is to satisfy the above mentioned needs in a cost-effective and optimized way.
The aforementioned aim is reached by an architecture for a dual clutch transmission and a related control method as claimed in the appended set of claims.
For a better understanding of the present invention, a preferred embodiment is described in the following, by way of a non-limiting example, with reference to the attached drawings wherein:
The transmission 1 essentially comprises, operatively connected in series one to the other between input shaft 2 and output shaft 3, an input stage A, a gear ratio stage B and a range gear ratio stage C.
The input stage A may be realized in different manner to provide torque to a first main clutch 5, hereinafter “forward clutch”, and torque in reversed direction to a second main clutch 6, hereinafter “rearward clutch”, both carried by the engine input shaft 2.
In disclosed exemplarily embodiment, input stage A comprises a gearing 4 comprising a first wheel 4′ configured to mesh with a first wheel 4a rotatably fixed to the forward clutch 5 and to a third wheel 4c configured to engage a second wheel 4b rotatably fixed to the rearward clutch 6.
As per se known, the forward clutch 5 couples the engine input shaft 2 to the output shaft 3 in order to allow a forward motion of the work vehicle while the rearward clutch 6 couples the engine input shaft 2 to the output shaft 3 in order to allow a rearward motion of the work vehicle. In the disclosed exemplarily embodiment, such occurrence is given by the peculiar construction of gearing 4 as described above.
Transmission 1 further comprise a first clutch 7, hereinafter “even clutch”, and a second clutch 8, hereinafter “odd clutch”. The even clutch 7 is configured to couple a first auxiliary shaft 11, hereinafter “even shaft”, with the forward clutch 5. The odd clutch 8 is configured to couple a first auxiliary shaft 12, hereinafter “odd shaft”, with the rearward clutch 6.
Advantageously, the forward clutch 5 is coupled to the even clutch 7 by a first housing 10′ and the rearward clutch 6 is coupled to the odd clutch 8 by a second housing 10″. The first and the second housing 10′, 10″ are coupled together by an intermediate gear 9, e.g. carried in a rotatable free manner by engine input shaft 2.
Preferably the intermediate gear 9 is configured to be coupled to the first housing 10′ through a first gear ratio and to be coupled to the second housing 10″ through a second gear ratio. The first and the second gear ratio are preferably different.
In view of above, thanks to the coupling of the housings 10′, 10″ with the intermediate gear 9, the even shaft 11 may be coupled to the rearward clutch 6 and the odd shaft 12 may be coupled to the forward clutch 5 according to their actuation.
The even shaft 11 and the odd shaft 12 each comprise a plurality of selection elements 17 e.g. synchronizer or dug clutches, fixedly carried by the respective shaft 11, 12 and therefore rotate together with to these latter. Obviously selection elements 17 may comprise other equivalent connection means such as joint clutches.
The gear ratio stage B comprises a plurality of gears 14, 15 accommodated on respectively even or odd shafts 11, 12 and having a different size one with respect to the other and that are supported in a rotatable free manner the respective shaft 11, 12, e.g. by means of bearings, so that they are not forced to rotate to the same speed of the respective shaft 11, 12 when the engaging dog clutch 17 is in their neutral position.
Preferably the even shaft 11 may comprise four gears 14, namely a first gear 14I having the biggest diameter, a fourth gear 14IV having the smallest diameter and a second and third gears 14II, 14III having respective diameters comprised between the ones of first and the fourth gears 14I, 14IV.
Similarly, the odd shaft 12 may comprise four gears 15, namely a first gear 15I having the biggest diameter, a fourth gear 15IV having the smallest diameter and a second and third gears 15II, 15III having respective diameters comprised between the ones of first and the fourth gears 15I, 15IV.
Advantageously the gear 14I has the same diameter of gear 15I, gear 14II has the same diameter of gear 15II, gear 14III has the same diameter of gear 15III and gear 14IV has the same diameter of gear 15IV.
The gears of gears sets 14, 15, when selected, represent the different speed ratios of the transmission; namely first speed ratio selecting gear 15I, second speed ratio selecting gear 14I, third speed ratio selecting gear 15II, fourth speed ratio selecting gear 14II, fifth speed ratio selecting gear 15III, sixth speed ratio selecting gear 14III, seventh speed ratio selecting gear 15IV or eighth speed ratio selecting gear 14IV.
As said above, gears of the gears sets 14, 15 may be selected by a dog clutch 17 configured to couple the shaft with the chosen gear. Preferably the even shaft 11 may comprise two dog clutches 17 interposed respectively between the gear 14I-14II and 14III-14IV. Similarly the odd shaft 12 may comprise two dog clutches 17 interposed respectively between the gear 15I-15II and 15III-15IV.
The transmission 1 further comprises an intermediate shaft 20 configured to engage with gear wheels 14, 15 and with gear range stage C. In particular, the intermediate shaft 20 is configured to carry a number of wheels 21 corresponding to the wheels of the gear ratio stage B.
It is noticed, even if visually schematized, that the intermediate shaft 20 is preferably arranged vertically adjacent, i.e. over/below, the even and odd shafts 11, 12 in order to provide a compact arrangement of the transmission 1.
Accordingly, intermediate shaft carries a first wheel 21I, a second wheel 21II, a third wheel 21III and a fourth wheel 21IV.
The gear range stage C is configured to engage a number of the wheels 21 carried by intermediate shaft 20 to the output shaft 3 by choosing among a plurality of gear ratios, defined by respective range gears 22, which are multiplied by the gear ratio of gear ratio stage B.
In the disclosed exemplarily embodiment, the gear range stage G comprises a first range gear 22I called “low” range, a second range gear 22II “medium” range, and a third range gear 22III called “fast”; the three range gears have different dimensions. In this way, the transmission provides twenty four possible gear ratios, due to the eight gear ratios repeated over the three range gear ratios.
According to the invention, the gear ratio wheels 22 are all carried in a rotatably free manner on a support shaft 23 and selectively engageable in rotation to this latter thanks to selection means 24 preferably design are semi-synchronizers.
Consequently, some of the wheels 21 carried by intermediate shaft 20 are carried in in a rotatably free manner on this latter and selectively engageable in rotation to this latter thanks to the aforementioned selection means 24.
The selection means 24 are controlled in order to allow a power shift change during gear shifting between gear wheels 14, 15 and/or range gear wheels 22 as detailed below.
In particular, the support shaft 23 is coupled to output shaft 3, e.g. via a gearing 30 comprising a first gear 30′ rigidly carried to the support shaft 23 and a second gear 30″ rigidly carried by output shaft 3.
In the disclosed embodiment, a pair of wheels 21 are carried in a rotatably free manner with respect to the intermediate shaft 20 and carrying respective range gears 22, in particular first wheel 21I carries first range gear 221 and fourth wheel 21IV carries third range gear 22III.
One of the wheel 21 is instead carried in a fixed manner with respect to intermediate shaft 20 and carries one range gear 22; in particular, second wheel 21I carries second range gear 22II.
The exceeding wheels of wheels 21 are preferably rotationally engaged with one of the wheels 21 carried in free manner by intermediate shaft 20. In particular, in the disclosed arrangement, third wheel 21III is rotationally fixed with respect to fourth wheel 21IV, i.e. they are carried by the same support that freely rotates on intermediate shaft 20.
Preferably, according to the shown embodiment, the wheels 21 are operatively connected to range gear wheels 22 via idler wheels 25. In particular, according to the above, each gear wheel 21 coupler to range gear wheel 22 is coupled by a respective idler wheel 25.
Preferably, each idler wheel 25 comprises a first wheel 25′ configured to engage with a respective gear wheel 21 and a second wheel 25″ configured to engage with a respective range gear wheel 22.
The above described clutches 5, 6, 7, 8, selection elements 17 and selection means 24 can be selected by respective actuators (not shown) that are controlled by an electronic control unit (not shown). The electronic control unit controls said clutches or said electronic motors by sending control electric signals directed to the respective clutches or motors to be controlled.
Electronic control unit can be either the ECU of the vehicle or driveline ECU of the vehicle. The electronic unit is configured to control the above cited elements of the transmission 1 as per direct input command of the user of the vehicle or in automatic way following the shift control logic deployed into a specific software code, which can be memorized into the electronic unit.
The operation of the transmission 1 according to the invention are described in the following.
In particular, the operation is described making the assumption that the transmission 1 is providing torque to output shaft 3 in the “first slow” gear ratio.
In a first example of operation, shown in
In a second example of operation, shown in
In a third example of operation, not shown in figures, it is described an upshift between to eight slow to first medium. In the initial condition, the torque flows from even shaft 11/wheel 14IV to range stage C passing via gear 21IV that free to rotate and makes rotate via idler gear 25 the wheel 22III that is coupled to support shaft 23.
Then, the wheels 22II and 14I are engaged via selection means 24/element 17 thereby allowing odd shaft 12 and intermediate shaft 20 rotate. Accordingly, clutches 8, 7 are swapped and torque passes through the new path defined by wheels 14I and range gear 22II via idler gear 25. When swapping is complete, wheels 15IV and 22III are disengage from the respective shafts 11, 23.
The vehicle may be provided by a dedicated control software code in the ECU of the transmission configured to recognize signals from sensors installed on the vehicle, e.g. the torque demand at the output shaft 3 and the speed of the engine input shaft 2, and automatically define the gearshift without any user intervention.
The invention also relates to a method for operating a transmission 1 as described above for shifting from a gear 14, 15 of a gear ratio stage B in combination a gear 22 of range gear stage C to a further gear 14, 15 of the gear ratio stage B in combination the gear 22 of range gear stage C:
In view of the foregoing, the advantages of a dual clutch transmission 1 according to the invention and the related method are apparent.
The transmission architecture 1 according to the invention increases the efficiency of the system. Indeed, the power losses due to the presence of clutches to allow power-shift between range gears is avoided.
Furthermore, the use of semi-synchronizers as selection means 24 provides a very compact and economic arrangement for coupling or uncoupling the support shaft gear wheels and range gear wheels.
It is furthermore noticed, that the range gear wheels may be designed smaller since the inertia carried by the range gear wheel is smaller with respect to known transmission architecture. Indeed the torque is split into different paths thanks to the specific arrangement of wheels on the intermediate shaft 20 and of the range wheels on the support shaft 23.
Since the clutch in range gears is not present and since the range gear wheels are smaller, the overall dimensions of the transmission 1 is more compact with respect to known architectures.
It is clear that modifications can be applied to the described transmission 1 which do not extend beyond the scope of protection defined by the claims.
For example, the number and typology of gears of gear ratio, range and idler gears may be varied according to vehicle necessity.
Further, the transmission may comprise different elements with respect to the described one, e.g. the number and/or typologies of clutches, gears and dog clutches may be varied. Accordingly, input stage A may be realized in any convenient manner.
Moreover, the control and typology of selection elements/means 17, 24 may be implemented with any typology of control, e.g. a hydraulic, electric or pneumatic in alternative or in combinations.
Number | Date | Country | Kind |
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102022000003782 | Mar 2022 | IT | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2023/055171 | 3/1/2023 | WO |