WO2002097300A1

WO2002097300A1 - Eight-speed motor vehicle gearbox

Info

Publication number: WO2002097300A1
Application number: PCT/PT2001/000027
Authority: WO
Inventors: José Manuel Braga Gomes ALBUQUERQUE
Original assignee: Albuquerque Jose Manuel Braga
Priority date: 2001-05-29
Filing date: 2001-10-29
Publication date: 2002-12-05
Also published as: WO2002097299A1; WO2002097301A1

Abstract

Eight-speed motor vehicle gearbox, plus four-speed reverse comprising a two basic modules gearbox each of the basic modules is composed of three gear wheels (6,8,10;7,9,11) by one shaft (12, 13) and by two conventional coupling and uncoupling systems (15, 17; 16, 18) combined with a conventional heavy-trucks double input splitter composed of two pairs of gearwheels (1, 2) (6, 7) and one main input shaft (3), one double coupling and uncoupling system (4) and a rigid connection (5) between gearwheels. The eight-speed gearbox also comprises a conventional three gearwheels reverse system (21). By means of the output splitter the gearwheels (10, 11) and the gearwheels (18, 20, 21) can be physically detached from the rest of the gearbox and those gearwheels can be theoretically stopped. This improves the gearbox mechanical efficiency and the fuel consumption economy on the three topgears, which are usually the vehicle's most used transmission gears.

Description

EIGHT-SPEED MOTOR VEHICLE GEARBOX

DESCRIPTION

The present invention relates to a eight-speed motor vehicle gearbox according to patent PCT/PTO 1/00009, titled "Method of construction of multi-speed motor vehicle gearboxes" and also according to patent PCT/PTO 1/00024, titled "Double input splitter application to method of construction of multi-speed motor vehicles gearboxes".

The previous patent PCT/PTO 1/00009 presented the original method of gearwheels disposal inside a gearbox. That patent is centralised in a basic module gear system, disposed in serial, whose aim is to achieve a bigger number of gear transmission ratios, then the allowed in the actual state of the art with a given number of gearwheels.

As a result of the following research and investigation on that innovative method, patent PCT/PT01/00009, the inventor have found that a real and feasible combination between torque capacity and gearbox actuation range interval is very difficult to achieve with the previous original method alone, patent PCT/PTO 1/00009.

As a solution, patent PCT/PTO 1/00024 introduced the combination of a "double input splitter" with patent PCT/PTO 1/00009 and solved the above mentioned problems related to the original method of construction of multi-speed motor vehicle gearboxes. That previous patent PCT/PTO 1/00024 basically describes a "three basic modules gearbox" combined with a double input splitter.

According to the present patent, that same double input splitter must be used to increase the working range of the gearbox, making the working range wider, within the torque capacity requirements needed to the gearbox components. Moreover, the double input splitter doubles the possible number of combinations of the original gearbox construction method.

The present patent of invention relates to a "two basic modules gearbox", instead of a "three basic modules gearbox", according to the original method, patent PCT/PTO 1/00009. According to the original patent, PCT/PTO 1/00009, a "three basic modules gearbox" has a total possible combination of nine different speed-gears. The combination of that gearbox with the double input splitter, according to patent PCT/PTO 1/00024, doubles the previous value to a total of eighteen final transmission ratios, or eighteen speed-gears.

With more research and more investigation on the gearbox final transmission ratios working range, the inventor found a feasible solution using a main core gearbox of only two basic modules, instead of three basic modules, according to the original patent PCT/PTO 1/00009, plus a double input splitter according to patent PCT/PTO 1/00024.

According to the original method considered alone, patent PCT/PTO 1/00009, the gearbox total number of transmission ratios is equal to the gearbox total number of basic modules squared. Hence, a "three basic modules gearbox" will have nine transmission ratios available and a "two basic modules gearbox" will have four transmission ratios available.

The combination of the original method with a double input splitter doubled the possible number of transmission ratios of the original gearbox construction method. Therefore, a "two basic modules gearbox" combined with a double input splitter will have eight transmission ratios available, or eight-speed gears.

The present invention relates to that eight-speed motor vehicle gearbox, composed of a "two basic modules gearbox" according to patent PCT/PTO 1/00009, combined with a double input splitter according to patent PCT/PTO 1/00024.

The innovative part of the present invention relates to a new reverse system and the possibility of a physical separation between the output shaft and the output gearwheel.

A new reverse system was required due to the very high relative speeds attained on the respective needle bearings of the previous reverse system, constructed according to patents PCT/PT01/00009 and PCT/PTO 1/00024. According to the present patent, the new reverse system is included within the gearbox main centre shafts, instead of using an independent and separated shaft for the reverse system. The new reverse system uses three gearwheels (19,20,21) instead of only two.

According to the previous mentioned patents, PCT/PTO 1/00009 and PCT/PTO 1/00024, the output shaft (14) and the output gearwheel (10) must be rigid one to another and constructed as a single part. Otherwise, the gearbox output shaft must be another independent shaft according to previous patents, PCT/PTO 1/00009 and PCT/PTO 1/00024.

According to the present patent of invention, the output shaft (14) is constructed as an independent part, relative to the respective output gearwheel (10). The new output shaft (14) and the new output gearwheel (10) work separately as an innovative "output splitter".

That innovative "output splitter" takes a great advantage on the main core gearbox working mechanism, by means of the possibility of detaching the output plane (III) gearwheels (10,11) and the reverse gearwheels (19,20,21) when they are not in use.

The output plane (III) gearwheels (10,11) must be used only on the gearbox first four lowest gears and they are not needed on the gearbox four top gears. The reverse gearwheels (19,20,21) are not needed when the vehicle is running forward. Therefore, those above- mentioned gearwheels can be detached from the gearbox main running mechanism and they can be theoretically stopped.

The right design of the reverse system, in combination with the gearbox output plane (III), leads to the possibility of detaching physically about forty percent of the gearwheels rotating mass. This greatly improves the gearbox mechanical efficiency on the vehicle's most used driving transmission ratios, leading to a long-term fuel consumption benefit.

According to the present patent, only six gearwheels (1,2,6,7,8,9) are needed for the four top consecutive gears. Notice that, a conventional five-speed gearbox has about thirteen gearwheels running on all transmission ratios. Therefore, six gearwheels are about fifty percent of the total number of gearwheels permanently running in a conventional five-speed gearbox. Therefore, the innovative "output splitter" is a great improvement in the gearbox mechanical efficiency.

The eight-speed gearbox described in this patent basically works the same way as described on the previous patents, PCT/PTO 1/00009 and PCT/PTO 1/00024.

According to patent PCT/PTO 1/00024, the double input splitter doubles the input possibilities of the original method and also overlaps two characteristic curves, by means of duplicating the characteristic curve attained by the original gearbox construction method, patent PCT/PTO 1/00009.

The present eight-speed motor vehicle gearbox also overlaps two characteristic curves at different levels, like is shown in Fig.l. Each of those two levels is a direct result of the use of two different input shaft rotations into the previous gearbox construction method, by means of the double input splitter.

BRIEF DESCRIPTION OF THE INVENTION

The present invention was found to be the best combination between a double input splitter, accordmg to patent PCT/PTO 1/00024, and a "two basic modules gearbox" constructed according to patent PCT/PTO 1/00009. Probably, it is also the simplest gearbox possible to attain with the original method, patent PCT/PTO 1/00009.

The double input splitter is composed of two gearwheel pairs (1,2) and (6,7), one main input shaft (3), one double synchronised tooth clutch (4) and a rigid connection (5) between gearwheels (2,7), as shown in Fig.3.

The "two basic modules gearbox" is composed of six gearwheels (6-11), two shafts (12,13) and four tooth clutch (15-18), meshing in serial according to patent PCT/PTO 1/00009, titled "method of construction of multi-speed motor vehicle gearboxes" . The gearwheel pair (6,7) is shared between the double input splitter and the input plane (I) of the innovative "two basic modules gearbox". Therefore, the gearwheels (6,7) belong to the double input splitter and, at the same time, they are the input plane (I) of the "two basic modules gearbox" .

That gearwheel pair (6,7) mean two different input levels within the "two basic modules gearbox", via the double input splitter gearwheel pair (1,2).

Those two different input levels are attained as follows. If the double synchronised tooth clutch (4) engages the input shaft (3) directly on to the gearwheel (6) of the input plane (I) , the "two basic modules gearbox" is driven by a direct connection between the vehicle engine and the "two basic modules gearbox" , producing the "high" input and the "high" characteristic transmission ratios curve shown in Fig. l.

If the double synchronised tooth clutch (4) engages the main input shaft (3) with the gearwheel (1) of the splitter, the engine rotation is driven to the "two basic modules gearbox" via the gearwheel (2). The gearwheel (2) diameter must be bigger then the gearwheel (1), in order to reduce the speed rotation transmitted to gearwheel (7) of the input plane (I) of the "two basic modules gearbox" . That reduced rotation speed produces the "low" input and the "low" characteristic transmission ratio curve shown in Fig. l .

In any of the cases, according to patent PCT/PTO 1/00009, the "two basic modules gearbox" will produce four transmission ratios. Thus, doubling the input possibilities by means of two different input levels, the result are eight possible combinations of transmission ratios on the output shaft (14) of the gearbox and a eight-speed gearbox.

By means of overlapping the two above mentioned characteristic curves, the gearbox range interval is a combined curve as shown in Fig.2. Using the right combination among all the gearwheel pairs that compose the present innovative gearbox, it is possible to attain equal speed-gear steps between all the eight transmission ratios of the gearbox. Fig. 2 shows the output transmission ratios of a gearbox whose speed-gear steps are all equal spaced between 24% and 25% more then the previous lower gear. Equal spaced transmission ratios means that, any value of any individual transmission ratio divided by the previous lower transmission ratio is constant value to all the gearbox transmission ratios.

FIELD OF THE INVENTION

The eight-speed gearbox, according to the present invention, applies to all type of motor vehicles, when a gearbox capable to provide multiple speed transmission ratios is needed.

The eight-speed gearbox, according to the present patent of invention, apply to heavy-trucks (using a conventional Range Section), light-trucks, small-trucks, vans, all type of automobiles and passenger vehicles, including all type of sport vehicles, up to the most powerful racing cars of any kind.

AIM OF THE INVENTION

The aim of the present invention was to present and describe a real and feasible eight-speed motor vehicle gearbox constructed according to the original and innovative method of construction, patent PCT/PTO 1/00009.

The eight-speed motor vehicle gearbox, according to the present patent of invention, probably is the simplest gearbox possible to attain with the original method, patent PCT/PT01/00009. Notice that, based on that original method, patent PCT/PTO 1/00009, it cannot be constructed gearboxes with less then two basic modules and, based on patent PCT/PTO 1/00024, a double input splitter is needed. Therefore, the present eight-speed gearbox is the smallest gearbox possible to construct with the innovative and original method of construction. BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in this patent of invention are schematic drawings of a real and feasible "two basic modules gearbox" constructed according to patent PCT/PTO 1/00009, combined with a double input splitter according to patent PCT/PTO 1/00024.

The drawings also describe a conventional three gearwheels reverse system and an innovative "output splitter", used to connect and disconnect the gearbox output plane (III) and all the reverse system, in order to improve fuel consumption.

Because any type of practical solution for the present invention demands that the profile and dimensions of all the teeth, used in the gearboxes, must be compatible with the needed number of teeth necessary to manufacture on each of the gearwheels, in the elaboration of the drawings included in this patent of invention the teeth number has been proportionally drawn for each of the gearwheels.

Fig.1 shows a graphic of the two different levels of the output range possible to attain by means of a double input splitter, with the same "two basic modules gearbox" .

Fig.2 is the same as Fig. l, but the graph values are ascending ordered. The graphic shown in Fig.2 corresponds to the final transmission ratios of the gearbox shown in Fig.3.

Fig.3 shows a schematic presentation of the basic working mechanism of a gearbox comprising two basic modules according to patent PCT/PTO 1/00009, plus a double input splitter mechanism according to patent PCT/PTO 1/00024, a conventional reverse system and an innovative "output splitter".

In order to the gearbox shown in Fig.3 produce the eight transmission ratios shown in Fig.1 and Fig.2, the respective gearwheels could be constructed as follows.

Gearwheel (1) - 20 teeth

Gearwheel (2) - 31 teeth

Gearwheel (6) - (22 teeth) must be equal to gearwheel (7) Gearwheel (7) - (22 teeth) must be equal to gearwheel (6) Gearwheel (8) - 20 teeth Gearwheel (9) - 30 teeth Gearwheel (10) - 31 teeth Gearwheel (11) - 16 teeth

The reverse gearwheels could be as follows. Gearwheel (19) - 28 teeth Gearwheel (20) - 14 teeth Gearwheel (21) - 14 teeth

In order to the eight transmission ratios be equal space, in a gearbox constructed according to the present patent, the gearwheels (6) and (7) must be equal sized. Therefore, the eight- speed gearbox shifting sequence must be always the same sequence as shown in Fig.4-11.

Fig.4 - Shows the gearbox first-gear engagement.

Fig.5 - Shows the gearbox second-gear engagement.

Fig.6 - Shows the gearbox third-gear engagement.

Fig.7 - Shows the gearbox fourth-gear engagement.

Fig.8 - Shows the gearbox fifth-gear engagement.

Fig.9 - Shows the gearbox sixth-gear engagement.

Fig.10 - Shows the gearbox seventh-gear engagement, a direct input-output.

Fig.11 - Shows the gearbox eighth-gear engagement.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a real, feasible and universal eight-speed motor vehicle gearbox according to Fig.3, comprising a serial association of two basic modules according to patent PCT/PTO 1/00009, in combination with a double input splitter according to patent PCT/PTO 1/00024, plus a conventional reverse system and an innovative "output splitter". The double input splitter doubles the input possibilities of the "two basic modules gearbox" . The double input splitter is used to attain a low level input and a high level input, on the "two basic modules gearbox". Those two different input levels are needed in order to solve the load capacity and range compatibility problems of the original method of construction of multi-speed motor vehicle gearboxes, patent PCT/PTO 1/00009.

The double input splitter working mechanism is the same of the input splitter system used on heavy-trucks gearboxes. The double input splitter is composed of two pairs of gearwheels (1,2) and (6,7), one main input shaft (3), one double synchronised tooth clutch (4) and a rigid connection (5) between gearwheels (2,7).

The gearwheel (1) is free to rotate on the main input shaft (3) and the gearwheel (1) can be coupled to the main input shaft (3) by means of the synchronised coupling and uncoupling system (4).

The double input splitter comprises the main input shaft (3), whose rotation permanently transmits the vehicle engine rotation to the double synchronised tooth clutch (4). That double synchronised tooth clutch (4) splits the engine rotation via the gearwheel (1) or the gearwheel (6).

The "two basic modules gearbox" is composed of six gearwheels (6-11), two shafts (12, 13) and four tooth clutch (15-18), meshing in serial according to patent PCT/PTO 1/00009, titled "Method of construction of multi-speed motor vehicle gearboxes".

The two gearwheels (6,7) are shared between the double input splitter and the input plane (I) of the "two basic modules gearbox". The gearwheels (6,7) belong to the double input splitter and, at the same time, they are the input plane (I) of the "two basic modules gearbox".

In order to the gearbox eight transmission ratios be equally spaced, those gearwheels (6) and (7) must be equal sized in any gearbox constructed according to the present patent. Therefore, the gearbox shifting sequence must be always the same sequence shown in Fig.4-11, to a gearbox constructed according to the present patent.

By means of the double input splitter, via the splitter gearwheel pair (1,2), the gearwheels (6) and (7) work as two different input levels in the input plane (I) of the "two basic modules gearbox", as follows.

The input via the gearwheel (6) is done by means of a direct coupling between the main input shaft (3) and the gearwheel (6). The gearwheel (6) belongs to the so-called "input plane" (I) of the "two basic modules gearbox". This coupling produces the high level input of the "two basic modules gearbox" shown in Fig.l.

The high input level on the gearbox is always a direct coupling, without any speed reduction between the main input shaft (3) and the "two basic modules gearbox" . That coupling is done by means of the double synchronised tooth clutch (4).

The input via the gearwheel (7) must be a reduced input level, in order to attain the lowest gearbox transmission ratio shown in Fig.l. That lowest transmission ratio is limited by the maximum admissible torque of the "two basic modules gearbox" components.

In order to attain the gearbox low input level via the gearwheel (7), the double synchronised tooth clutch (4) must be actuated in opposite direction, coupling the main input shaft (3) with the gearwheel (1) of the splitter system. The gearwheel (1) meshes with the gearwheel (2) and the gearwheel (2) must be bigger then gearwheel (1), in order to reduce the main input shaft (3) speed.

The gearwheel (2) is rigidly fixed to gearwheel (7), via the rigid connection (5). Thus, the input transmitted to the gearwheel (7) of the "two basic modules gearbox" is a reduced level. Those gearwheels (2,7) must rotate freely on the respective shaft (13) in order to meet the requirements of the original method of construction of gearboxes, according to patent PCT/PTO 1/00009. The "two basic modules gearbox" is the main core of the present eight-speed gearbox invention, according to patent PCT/PTO 1/00009. It cannot be removed any component, or changed the basic working mechanism, of the "two basic modules gearbox", according to patent PCT/PTO 1/00009.

The innovative "two basic modules gearbox" works differently then any conventional motor vehicle gearbox. In a conventional gearbox, the majority of the gearwheels and the majority of the synchronised tooth clutch only produce one gear transmission. If a double input splitter is used, like in the conventional heavy-trucks gearbox, each gearwheel pair can produce two transmission gears maximum.

Somehow, a conventional motor vehicle gearbox always need to perform a primary reduction, between the input shaft and the countershaft, in order to attain the lowest gearbox reduction ratio, or the first-gear. It was found that the same is needed for the innovative gearbox construction method, patent PCT/PTO 1/00009. That is the reason why a "two basic modules gearbox" needs a double input splitter according to the present patent.

In a conventional motor vehicle gearbox there is always at least one countershaft. The countershaft is composed of several gearwheels rigidly fixed to a shaft. "Countershaft" means a shaft with more then one gearwheel rigid to that shaft. The countershaft rigid gearwheels drive the possible output gearwheels at different speed rotation.

According to the original innovative method of construction of multi-speed motor vehicle gearboxes, patent PCT/PTO 1/00009, it is a primary condition of that method that, any of the two main shafts (12,13) of "two basic modules gearbox" cannot have more then one gearwheel rigidly fixed to the respective shaft. It is also a primary condition that the two gearwheels (8,9), which are rigidly fixed to the respective shafts (12,13), must lie in the same plane, (I), (II), or (III), meshing with one another.

The above two conditions have introduced the new concept of "gearbox planes" . There are always three planes (I,II,III) according to the innovative method, patent PCT/PTO 1/00009. The so-called input plane (I) is composed by the two gearwheels (6,7) that are free to rotate on the respective shaft (12,13). The so-called central plane (II) is composed of the two gearwheels (8,9) that must be rigidly fixed to the respective shafts (12,13). Finally, the so- called output plane (III) is composed by the two gearwheels (10,11) that are free to rotate on the respective shafts (12,13) of the "two basic modules gearbox" .

The main difference, between a conventional gearbox and the present innovative eight-speed gearbox, is the fact that a conventional gearbox is based on the countershaft driving free gearwheels at different speeds, and the present innovative eight-gearbox is based on three different gearwheels planes (I, II, III) rotating at different speeds, as shown is Fig.3.

The present eight-speed gearbox is the simplest combination possible between the original method of construction of multi-speed motor vehicles gearboxes, patent PCT/PTO 1/00009, and a conventional double input splitter according to patent PCT/PTO 1/00024.

In order to attain the necessary working range of the great majority of motor vehicles, and equal step ratios between all the gearbox speed-gears, the present eight-speed gearbox events shifting sequence must be as shown in Fig.4-11.

According to Fig.3, the present eight-speed gearbox comprises two double synchronised tooth clutch (4) and (17), two single synchronised tooth clutch (15) and (16), and two single unsynchronised tooth clutch (18) and (23). "Single tooth clutch" means that the tooth clutch only have one gearwheel coupling possibility. "Double tooth clutch" means that the tooth clutch have two alternatively gearwheel coupling possibilities.

Only the two single unsynchronised tooth clutch (18) and (23) can be altered. Both single unsynchronised tooth clutch (18) and (23) can be replaced by only one double tooth clutch, synchronised or unsynchronised, rigidly connected to the shaft (13), and positioned between the gearwheels (11) and (20). If that double tooth clutch is used, instead of the two single unsynchronised tooth clutch (18) and (23), the gearbox total length will increase. This type of coupling and uncoupling solution can be chosen if necessary, without any change in the basic working mechanism of the present eight-speed gearbox. The present eight-speed gearbox lowest gear, the first-gear, is attained via the double input splitter low input. In the first-gear the double synchronised tooth clutch (4) must be actuated in order to couple the main input shaft (3) with the gearwheel (1), driving the engine torque to the gearwheel (2). The gearwheel (2) is rigidly coupled to gearwheel (7) of the input plane (I) of the "two basic modules gearbox".

Within the "two basic modules gearbox", to engage the gearbox first-gear, the single synchronised tooth clutch (15) must couple the gearwheel (6) with gearwheel (8), between the input plane (I) and the central plane (II), and the single unsynchronised tooth clutch (18) must couple the gearwheel (9) with gearwheel (11), between the central plane (II) and the output plane (III).

In the gearbox first-gear, the output shaft (14) must be driven via the so-called output gearwheel (10) of the "two basic modules gearbox" . In order to do that, the double synchronised tooth clutch (17) must be actuated in order to couple the gearbox output shaft (14) with the so-called output gearwheel (10).

According to the previous mentioned patents, PCT/PTO 1/00009 and PCT/PTO 1/00024, the output shaft (14) and the output gearwheel (10) are rigid to one another and constructed as a single part. Otherwise, according to those previous patents, the gearbox output shaft must be another independent shaft, driven by another external gearwheel.

According to the present patent of invention, the output shaft (14) must be constructed as an independent part relative to the output gearwheel (10). The new output shaft (14) and the new output gearwheel (10) work separately as an innovative "output splitter".

Fig.4 schematically shows the engine torque transmission, along the present eight-speed gearbox, in the gearbox first-gear. Fig. shows the same as Fig.4 for the gearbox second- gear engagement. Fig.6 shows the gearbox third-gear engagement. Fig.7 shows the gearbox fourth-gear. Fig.8 shows the gearbox fifth-gear. Fig.9 shows the gearbox sixth-gear. Fig.10 shows the gearbox seventh-gear. And finally, the Fig.11 shows the gearbox top gear, the eight-gear engagement. The gearbox second-gear uses the same low input splitter, as the first-gear does, and also the same output gearwheel (10), as the first-gear does. Thus, the two double synchronised tooth clutch (4) and (17) could stay in the same previous coupled position when shifting between the first and second-gears. Also, in second-gear the single unsynchronised tooth clutch (18) must stay in the same position between the first and second-gears.

In fact, the single unsynchronised tooth clutch (18) and the double tooth clutch (17) must stay coupled in the same position to all the four lowest gearbox transmission ratios, as shown in Fig.4-7.

To all the remaining gearbox gears, called the four top gears and shown in Fig.8-11, the double synchronised tooth clutch (17) must be actuated in the opposite direction, in order to couple the gearbox output shaft (14) directly with the gearwheel (8).

Also, to all the gearbox four top gears shown in Fig.8-11, the single unsynchronised tooth clutch (18) could be actuated, or not. The fact that the single unsynchronised tooth clutch (18) could be both positions, actuated or not actuated, is possible because the new output shaft (14) and the new output gearwheel (10) work separately as an innovative "output splitter".

The "output splitter" is composed of a independent gearbox output shaft (14) with a double synchronised tooth clutch (17) rigidly connected to that output shaft (14). The "output splitter" also comprises the two gearwheels (10,19) that are rigidly connected to one another and free to rotate on the output shaft (14), plus the independent gearwheels (11) and (20) that are both free to rotate on the shaft (13).

The two gearwheel (11) and (20) can be coupled and uncoupled to the respective shaft (13) by means of tooth clutch (18) and (23). The two gearwheels (10) and (11) are shared between the "output splitter" and the so-called output plane (III) of the "two basic modules gearbox". The two gearwheels (19) and (20) of the "output splitter" belong to the reverse system. In the gearbox four top gears, if the single unsynchronised tooth clutch (18) is not actuated (open), then the two gearwheels (10,11) of the output plane (III), plus the gearwheels (19,20,21) of the reverse system, are physically detached from the rest of the gearbox. Those gearwheels can be theoretically stopped.

According to the present patent of invention, only six gearwheels (1,2,6,7,8,9) are needed for the gearbox four top consecutive gears, as shown in Fig.8-11. This greatly improves the gearbox mechanical efficiency on the vehicle's most used driving transmission ratios, leading to a long-term fuel consumption benefit.

In fact, according to the present patent, the eight-speed gearbox is somehow divided between the four lowest gears and the four top gears. The gearbox four lowest gears are attained via the gearwheel pair (10,11) and the four top gears are a direct coupling between the output shaft (14) and the gearbox central plane (II), via the gearwheel (8).

According to this above-mentioned characteristic of the present eight-speed gearbox, between the gearbox first and second-gears only the two single synchronised tooth clutch

(15) and (16) must change the relative position. Between the gearbox second and third-gear those two single synchronised tooth clutch (15) and (16) must change relative position once again.

In fact, among the total of seven shifting gear, that are mathematically possible with the present eight-speed gearbox invention, the two single synchronised tooth clutch (15) and

(16) must change relative position in all of the seven possible shifting gear of the present eight-speed gearbox.

This above mentioned characteristic of the present eight-speed gearbox, concerning the two single synchronised tooth clutch (15) and (16), is very important. Because the two single synchronised tooth clutch (15) and (16) must always change relative position when shifting, these two tooth clutch (15) and (16) must be the last ones to be coupled if the present eight- speed gearbox is aimed to be a manual gearbox, directly actuated by the vehicle's driver. If the present eight-speed gearbox is aimed to be a manual gearbox, directly actuated by the driver by means of a fully mechanical and direct system to the gearbox, then the two single tooth clutch (15) and (16) must be bigger then represented in Fig.3. They must have a bigger diameter because they must be the last ones to be coupled and they must attain the final vehicle's engine speed change.

If the two single tooth clutch (15) and (16) need to be bigger they cannot be positioned inline, as shown in Fig.3. In the case of a manual gearbox, according to the present patent, the two single tooth clutch (15) and (16) need to be bigger and they must be positioned side by side, in terms that the total length of the gearbox must increase.

Thus, the eight-speed gearbox described in Fig.3 is aimed to be a fully automated gearbox. In a fully automated eight-speed gearbox, according to the present patent, the last tooth clutch to be coupled must be the double synchronised tooth clutch (4).

If the present eight-speed gearbox is aimed to be a fully automated gearbox, according to Fig.3, the gearbox tooth clutch coupling sequence could be different then in a manual gearbox. According to the engineered design of the eight-speed gearbox shown in Fig.3, the two single synchronised tooth clutch (15) and (16) could be small enough to be positioned inline.

According to the fully automated eight-speed gearbox shown in Fig.3, the gearbox first movement on any of the seven possible gearbox shifting gear must be the return of the double synchronised tooth clutch (4) to it's neutral position, leaving all the gearbox rotating mass free from the input shaft (3) that is driven from vehicle's engine. Second, the single unsynchronised tooth clutch (18) must be coupled if necessary. Third, the synchronised double tooth clutch (17) must be coupled according if necessary. Fourth, the two single synchronised tooth clutch (15) and (16) must change position respectively. Finally, the double synchronised tooth clutch (4) must be the last one to be coupled.

The tooth clutch coupling sequence depends on the gearbox kinetic energy change between shifts, and involves mass inertia moments and rotation speed change calculations. It was found that gearbox global rotation speed changes are smooth between six of the seven total gearbox-shifting possibilities. But the shifting gear between the fourth and the fifth- gear produces a very high global gearbox speed change.

A difficult shift between the fourth-gear and the fifth-gear is one of the major characteristics of the present eight-speed gearbox invention. That characteristic is the most important engineering problem of this gearbox and it must be very carefully addressed in the gearbox design according to the present patent.

The most critical result of that above-mentioned problem occurs in the downshift between the fifth-gear and the fourth-gear. That shifting will take more time to be concluded then any other gearbox shifting, and also more time then it is normal in a conventional gearbox shifting.

In general, according to the present eight-speed gearbox invention, the shifting events can be described as follows.

The two single synchronised tooth clutch (15) and (16) must change relative position in all the seven possible shifting gears of the eight-speed gearbox. The double synchronised tooth clutch (17) must be always coupled and only changes position between the gearbox fourth and the fifth-gear. The double synchronised tooth clutch (4) must be always coupled and only changes position three times: between the second and the third-gear, between the fourth and the fifth-gear and between the sixth and the seventh-gear.

The two single unsynchronised tooth clutch (18) and (23) are not active tooth clutch. This means that they do not need to change position in a normal shifting sequence. According to the present invention, those two single unsynchronised tooth clutch (18) and (23) must be always previously engaged and they cannot be engaged at the same time.

The single unsynchronised tooth clutch (23) belongs to the reverse system. Therefore, the single unsynchronised tooth clutch (23) must be coupled only to vehicle's reverse. The single unsynchronised tooth clutch (18) could be always coupled, as previously mentioned. In fact, the single unsynchronised tooth clutch (18) could be dispensable on the present eight-speed gearbox, because it is not needed in the basic gearbox working mechanism. The gearwheel (11) could be rigidly and permanently fixed to the shaft (13).

This important characteristic of the present eight-speed gearbox, concerning the tooth clutch (18), is a direct consequence of the so-called "output splitter", as previously described. Also, this important characteristic of the present eight-speed gearbox is possible because an "output splitter" is used. Otherwise, the tooth clutch (18) must work according to the original method, patent PCT/PTO 1/00009.

It was aim of the present invention to take advantage of the above-mentioned characteristic concerning the single unsynchronised tooth clutch (18). That advantage is the fact that, in the present gearbox four top gears, the two gearwheels (10,11) of the output plane (III), plus the gearwheels (19,20,21) of the reverse system, can be physically detached from the rest of the gearbox. Those gearwheels can be theoretically stopped. This greatly improves the gearbox mechanical efficiency on the vehicle's most used driving transmission ratios, leading to a long-term fuel consumption benefit.

In vehicle's normal running, the single unsynchronised tooth clutch (18) only needs to be changed once, on the downshift between the fifth and fourth-gear, according to Fig.8 and Fig.7. In order to avoid the need of a big and expensive active synchronised tooth clutch to do that specific downshift, instead it is used a small single unsynchronised tooth clutch (18), with the condition that the single unsynchronised tooth clutch (18) must be previously engaged between the sixth to fifth-gear downshift.

According to the present patent of invention, the single unsynchronised tooth clutch (18) must be automatically engaged on the previous downshift between the sixth and the fifth- gear. If so, when the next downshift occurs, from the fifth to fourth-gear, the single unsynchronised tooth clutch (18) is already engaged. According to the above working mechanism, the present eight-speed gearbox can take use of the previously mentioned advantage, concerning the physical detachment of several gearwheels. Therefore, the present eight-speed gearbox is a very competitive gearbox in terms of mechanical efficiency and fuel consumption economy.

A reverse system is also included in this patent of invention. The best solution for the reverse system, found by the inventor, is a conventional reverse system described in Fig.3. It is an additional gearwheel system, making use of the existing main core gearbox shafts (13,14) plus one small extra shaft (22), like in a conventional gearbox.

According to the present patent, the reverse system is very similar to a conventional reverse system, comprising three gearwheels (19,20,21) free to rotate on the respective shaft (13,14,22), one small independent shaft (22) and a coupling and uncoupling system (23). In order to meet the previously mentioned "output splitter" requirements, the gearwheel (19) is rigidly connected to the so-called output gearwheel (10) and both rotate freely on the output shaft (14).

The gearwheel (19) mesh with the gearwheel (21) and the gearwheel (21) mesh with the gearwheel (20). The gearwheel (21) is an intermediate gearwheel that rotates free on the small independent shaft (22) of the reverse system.

In order to reverse, the gearbox actuation must be the same sequence used for the gearbox four lowest gears forward. The only exception is the coupling change between the single unsynchronised tooth clutch (18) and the single unsynchronised tooth clutch (23).

According to the present patent of invention, the single unsynchronised tooth clutch (23) is used for reverse and the single unsynchronised tooth clutch (18) is used to run forward. Both cannot be used at the same time. This is the reason why one double tooth clutch could be used instead of the two different tooth clutch (18) and (23), as previously mentioned.

Claims

1. Eight-speed motor vehicle gearbox, comprising a "two basic modules gearbox" according to patent PCT/PTO 1/00009, in combination with a conventional "double input splitter" according to patent PCT/PTO 1/00024, plus an innovative "output splitter" and a conventional reverse system.

The "double input splitter" is composed by two pairs of gearwheels (1,2) and (6,7), one main input shaft (3), one double synchronised tooth clutch (4) and a rigid connection (5) between the two gearwheels (2,7). The gearwheel (1) is free to rotate on the main input shaft (3) and the gearwheel (1) can be coupled to the main input shaft (3) by means of the double synchronised tooth clutch (4). The main input shaft (3) receives rotation from vehicle's engine and permanently transmits the vehicle engine rotation to the double synchronised tooth clutch (4). The double synchronised tooth clutch (4) splits the vehicle's engine rotation via the gearwheel (1) or the gearwheel (6).

The "two basic modules gearbox" is composed of six gearwheels (6-11), two shafts (12,13) and four tooth clutch (15-18). The "two basic modules gearbox" is constructed according to patent PCT/PTO 1/00009, titled "method of construction of multi-speed motor vehicle gearboxes" . The "two basic modules gearbox" is composed by three planes (I, II, III) according to the innovative method, patent PCT/PTO 1/00009. The so-called input plane (I) is composed by the two gearwheels (6,7) that are free to rotate on the respective shaft (12,13). The so-called central plane (II) is composed by the two gearwheels (8,9) rigidly fixed to the respective shafts (12,13). Finally, the so-called output plane (III) is composed by the two gearwheels (10,11) that are free to rotate on the respective shafts (12, 13) of the "two basic modules gearbox" .

The two gearwheels (6,7) are shared between the double input splitter and the input plane (I) of the "two basic modules gearbox". The gearwheels (6,7) belong to the double input splitter and, at the same time, the two gearwheels (6,7) are the input plane (I) of the "two basic modules gearbox" .

The "output splitter" is composed by a completely independent output shaft (14), with a double synchronised tooth clutch (17) rigidly connect to that output shaft (14). The "output splitter" also comprises the two gearwheels (10,19) that are rigidly connect to one another and free to rotate on the output shaft (14), plus the independent gearwheels (11) and (20) that are both free to rotate on the shaft (13). The two gearwheels (11) and (20) can be coupled and uncoupled to the respective shaft (13) by means of tooth clutch (18) and (23). The two gearwheels (10,11) are shared between the "output splitter" and the so-called output plane (III) of the "two basic modules gearbox". The two gearwheels (19,20) of the "output splitter" also belong to the reverse system.

2. Gearbox according to Claim 1, characterised in that the combination between a "two basic modules gearbox" and a conventional "double input splitter" produces eight different speed-gears forward plus four different speed-gears reverse.

3. Gearbox according to Claim 1, characterised in that, by means of the two tooth clutch (17) and (18), the two gearwheels (10, 11) of the output plane (III), plus the gearwheels (19,20,21) of the reverse system, can be physically detached from the rest of the gearbox and those mentioned gearwheels can be theoretically stopped.