GB2478297A - Planetary gearbox with a hill hold function, the output shaft being locked by at least one clutch - Google Patents

Abstract

A method of using a transmission 10 to provide a hill hold gear ratio. The transmission 10 comprises a plurality of planetary gear sets 15, 16, 17, 18, a casing 20, and one or more clutches CB1278R, CB12345R, C13567, C23468, C45678R for providing forward and reverse gear ratios of the transmission 10. The method comprises a step of engaging the clutches CB1278R, CB12345R, C13567, C23468, C45678R to lock an output shaft 13. The output shaft 13 is connected to one of the planetary gear sets 15, 16, 17, 18.

Description

Use of a hill-hold ratio on an automatic transmission family The present application relates to a hill hold function of a vehicle. In particular, the application relates to a hill hold function that is provided by a transmission of the vehicle.

A passenger vehicle includes a powertrain that comprises an engine, a multi-speed transmission, and a differential or fi-nal drive. The multi-speed transmission increases an overall operating range of the vehicles by permitting the engine to operate through its torque range over different speed ranges.

This also improves operating performance and fuel economy of the vehicle.

Six-speed transmissions offer several advantages over four and five speed transmissions, including improved vehicle accelera-tion and improved fuel economy. However, as the number of transmission speed increases, size, complexity, and cost of the transmission also increases.

It is an object of this application to provide a hill hold function of a vehicle at a low cost.

One of the main thoughts of this application is that a locking state of an engine transmission can serve to provide a hill-hold function. Specifically, gears and planetary gear sets that are used to provide forward and reverse gear ratios can also be used to provide the hill hold function without any ad- ditional hardware. Such an implementation provides the hill-hold function at a low cost that would benefit many users.

This application provides a hill-hold gear ratio for an engine transmission.

The engine transmission can serve a rear-wheel drive vehicle.

In the rear-wheel drive vehicle, the engine transmission is positioned between front wheels and rear wheels of the vehi-cle. The transmission can have eight forward gear ratios and one reverse gear ratio that are obtained by applying or by controlling three transmission clutches.

The hill-hold gear ratio locks the engine transmission such that gear wheels of the engine transmission cannot turn. In other words, the said lock also prevents the vehicle from mov-ing backwards when the vehicle stops temporarily in the middle of a slope. The locking state can be achieved by just one clutch engagement. Put differently, a transition to the lock- ing state can require an engagement of just one clutch. Spe-cifically, the transmission can shift directly from a first, a second, or a third gear ratio to the hill-hold gear ratio.

This way of preventing the vehicle from moving is directly in-tegrated with the transmission and it does not require other implementations, such as an application of brakes or addi-tional hardware.

The application provides a method of using a transmission to provide a hill hold gear ratio.

The transmission includes a plurality of planetary gear sets, a casing, and one or more clutches. Each planetary gear set comprises a ring gear, a sun gear, and a planetary carrier.

The casing is used for housing the planetary gear sets. The clutches are intended for providing different forward and re-verse gear ratios of the transmission. This said gear ratios r are achieved by connecting parts of the planetary gear sets to the casing and to other parts of the planetary gear sets.

The method includes a step of activating or applying the clutches in order to lock an output shaft that is connected to one part of the planetary gear sets. The locking provides the output staff from turning, which in turn keeps wheels of a ye-hide that is installed with the transmission from moving backward and from moving forward.

When the clutch is activated, the clutch closes such that a first element that is connected to a first end of the clutch is connected to a second element that is connected to a second end of the clutch.

The method has an advantage in that it does not require any hardware modification for its implementation. The method is merely applied on planetary gear sets, casing, and clutches that are used for provided the various forward and reverse gear ratios.

In one implementation, to provide the hill hold gear ratio, the step of activation comprises -activating a first clutch to engage a first ring gear of a first planetary gear set with the casing, -activating via a second clutch to engage a first sun gear of the first planetary gear set with the casing, -activating a third clutch and a fourth clutch to engage a second ring gear of a second planetary gear set with a second planetary carrier of the second planetary gear set, and -activating the third clutch to engage a fourth sun gear of the fourth planetary gear set with the second ring gear.

The above steps are characterised in that -the second sun gear is engaged with the first sun gear, -a third sun gear of a third planetary gear set is engaged with the second ring gear, -a fourth ring gear of a fourth planetary gear set is en-gaged with the first planetary carrier, and -a fourth planetary carrier of the fourth planetary gear set is connected to the output shaft.

An input shaft can be connected to the second planetary car-rier.

In addition, the step of the activating can further include activating a fourth clutch to engage a third ring gear of the third planetary gear set to the fourth sun gear, wherein a planetary carrier is connected to the fourth planetary car-rier.

The step of the activating can also further comprise activat-ing a fourth clutch to engage the planetary carrier with the fourth planetary carrier.

In the following description, details are provided to describe embodiments of the application. It shall be apparent to one skilled in the art, however, that the embodiments may be prac-tised without such details.

Fig. 1 illustrates a stick diagram of an embodiment of a first transmission, Fig. 2 illustrates a table of friction elements of the first transmission of Fig. 1, Fig. 3 illustrates a torque flow of a hill hold gear ratio of the first transmission, Fig. 4 illustrates a stick diagram of an embodiment of a second transmission, and Fig. 5 illustrates a table of friction elements of the sec-ond transmission of Fig. 4.

Figs. 1 to 5 have similar parts. The similar parts have same names or similar part numbers. The description of the similar parts is hereby incorporated by reference, where appropriate, thereby reducing repetition of text without limiting the dis-closure.

Fig. 1 shows a stick diagram of an embodiment of a first transmission 10. The first transmission 10 includes an input shaft 12 and an output shaft 13. The input shaft 12 and the output shaft 13 lies in a same longitudinal axis.

A plurality of gear sets is positioned between the input shaft 12 and the output shaft 13 and it is joined to the input shaft 12 and to the output shaft 13. The plurality of gear sets com-prises a first gear set 15, a second gear set 16, a third gear set 17, and a fourth gear set 18. A casing 20 houses the input shaft 12, the output shaft 13, and the gear sets 15, 16, 17, and 18.

The first gear set 15 is provided next to the fourth gear set 18 and next to the second gear set 16 whilst the third gear set 17 is provided next to the second gear set 16.

The first gear set 16 comprises a plurality of first planetary gears that meshes with a first ring gear Ri and with a first sun gear Sl. The first planetary gears are jointed to a first planetary carrier PCi.

Similarly, the second gear set 17 comprises a plurality of second planetary gears that meshes with a second ring gear R2 and with a second sun gear S2. The second planetary gears are jointed to a second planetary carrier PC2. The third gear set 18 comprises a plurality of third planetary gears that meshes with a third ring gear R3 and with a third sun gear S3. The r third planetary gears are jointed to a third planetary carrier PC3. The fourth gear set 19 comprises a plurality of fourth planetary gears that meshes with a fourth ring gear R4 and with a fourth sun gear S4. The fourth planetary gears are jointed to a fourth planetary carrier P04.

Referring to the first gear set 15, the first planetary car-rier PCi is fixed to the fourth ring gear R4. The first ring gear Ri is selectively fixed to the casing 20 via a clutch CB12345R. The first sun gear 1 is selectively fixed to the casing 20 via a clutch CB1278R and it is fixed to the second sun gear S2.

Referring to the second gear set 16, the second planetary car-rier PC2 is fixed to the input shaft 12 and it is selectively fixed to the fourth sun gear S4 of the fourth gear set 18 via a clutch 013567. The second ring gear R2 is fixed to the third sun gear S3 and it is selectively fixed to the fourth sun gear S4 via a clutch 023468.

Referring to the third gear set 17, the third planetary car-rier PC3 is fixed to the fourth planetary carrier PC4. The third ring gear R3 is selectively fixed to the fourth sun gear S4 via a clutch C45678R. The third sun gear S3 is selectively fixed to the fourth sun gear S4 via the clutch 023468.

Referring to the fourth gear set 18, the fourth planetary car-rier P04 is fixed to the output shaft 13.

In practise, the input shaft 12 receives a rotating force from an engine of a vehicle via a torque converter. The engine, as provided here, refers either to a combustion engine or to an electrical engine. The output shaft 13 turns wheels of a vehi-cle via a differential.

The clutches 013567, 023468, C45678R, CB1278R, and CB12345R can be closed or open. The clutch closing is also called an clutch engagement or an application of the clutch. Similarly, the clutch opening is also called a disengagement of clutch.

The closed clutches C13567, 023468, C45678R, CB1278R, and CB12345R connect one part of the transmission 10 to another part of the transmission 10. Specifically, the closed clutches CB1278R and CB12345R connect the casing 20 to one or two sun gears. In effect, the closed clutch C51278R stops the sun gears Si and S2 from turning. Likewise, closed clutch CB12345R stops the first ring gear Ri from turning. In a generic sense, a band or a brake can replace the clutches CB1278R and CB12345R for performing the same functions.

The different closed and open state of the various clutches Cl3567, 023468, C45678R, CB1278R, and CB12345R allows the transmission 10 to provide a hill hold gear ratio and other different gear ratios. The other different gear ratios include eight forward gear ratios, one reverse gear ratio, and one neutral gear ratio. The hill hold gear ratio is also called a stand gear ratio or a stand gear state. The hill-hold gear ra-tio prevents the output shaft 13 from turning. This is useful for preventing a vehicle with the transmission 10 from moving backward or forward when the vehicle stops in the middle of a slope.

The gear sets 15, 16, 17, and 18 each can provide a speed ra-tio when one of its member gears is fixed and another of its member gears is driven.

Operationally, a transition between adjacent active gear ra-tios can need just one clutch-to-clutch change, as illustrated in Fig. 2. The clutch-to-clutch change refers to engagement of one other gear wheel and the disengagement of another gear wheel.

Referring to the hill hold gear ratio, this is achieved by en-gaging the clutches CB1278R, OB12345R, 023468, and 045678R, as illustrated in Fig 2. The clutch engagement locks or fixes the output shaft 13 to the casing 20, which thereby prevents the output shaft 13 from turning. A torque flow of the transmis-sion with the hill hold gear ratio is illustrated in Fig. 3.

As seen in the first gear set 15 of Fig. 3, the first ring gear Ri is fixed to the casing 20 via the engaged clutch 0B12345R whilst the first sun gear Si is fixed to the casing via the engaged clutch CB1278R. Because of this, the first planetary carrier P01 is kept stationary, which in turn also keeps the fourth ring gear R4 stationary.

As seen in the second gear set 16 of Fig. 3, the second ring gear R2 is fixed to the second planetary carrier P02 via the engaged clutches 013567 and C45678R whilst the second sun gear S2 is fixed to the casing 20 via the engaged clutch 081278R.

This fixes the second ring gear R2, the second planetary car- rier P02, and the second sun gear S2, to each other and pre-vents them from moving. This in turn also keeps the fourth sun gear S4, which is fixed to the second planetary carrier P02, from moving.

Since the fourth ring gear R4 and the fourth sun gear S4 are kept stationary, the fourth planetary carrier PC4 is also kept from moving. The output shaft 13, which is fixed to the fourth planetary carrier P04, is then kept from moving. In this man-ner, the hill hold gear ratio is realized.

The hill hold gear ratio, as is implemented here, is inte-grated with the other functions of the transmission 10. Thus, not additional hardware is required for its implementation.

Thus, the embodiment has an advantage of realising the hill hold gear ratio at a low cost.

s Referring to the reverse gear ratio, this is achieved by en- gaging the clutches CB1278R, CB12345R, and C45678R, as illus-trated in Fig 2. The reverse gear ratio can transit to the hill-hold gear ratio by transiting initially to the first gear ratio by disengaging the clutch C45678R and by engaging the clutch C13567. Then, a transition is made from the first gear ratio to the hill hold gear ratio by engaging the clutch C23468.

Referring to the neutral gear ratio, this is achieved by en-gaging the clutches CB1278R and C12345R, as illustrated in Fig 2. Engaging the clutches CB1278R and C12345R is insufficient to provide a gear ratio for transmitting torque. These two clutches CB1278R and C12345R are also engaged in the reverse gear ratio and the first gear ratio. This means that, from the neutral gear ratio, an engagement of the clutch C13567 would realise the first gear ratio whilst an engagement of the clutch C45678R would realise the reverse gear ratio.

Referring to the first gear ratio, this is achieved by engag-ing the clutches CB1278R, CB12345R, and C13567, as illustrated in Fig 2. To transit or move from the reverse gear ratio to the hill hold gear ratio, the clutch C45678R is disengaged and the clutch C13567 is engaged. The first gear ratio can transit directly to the hill hold gear ratio just by engaging the clutch C23468.

Referring to the second gear ratio, this is achieved by engag-ing the clutches CB1278R, CB12345R, and C23468, as illustrated in Fig 2. To transit or move from the first gear ratio to the -10 -second gear ratio, the clutch 013567 is disengaged and the clutch C23468 is engaged.

Referring to the third gear ratio, this is achieved by engag-ing the clutches CB12345R, 023468, and C13567 are engaged, as illustrated in Fig 2. To transit or move from the second gear ratio to the third gear ratio, the clutch CB1278R is disen-gaged and the clutch 013567 is engaged.

Referring to the fourth gear ratio, this is achieved by engag-ing the clutches CB12345R, 023468, and C45678R, as illustrated in Fig 2. To transit or move from the third ratio to the fourth gear ratio, the clutch C13567 is disengaged and the clutch C45678R is engaged.

Referring to the fifth gear ratio, this is achieved by engag-ing the clutches CB12345R, 013567, and C45678R, as illustrated in Fig 2. To transit or move from the fourth gear ratio to the fifth gear ratio, the clutch 023468 is disengaged and the clutch C13567 is engaged.

Referring to the sixth gear ratio, this is achieved by engag-ing the clutches 023468, 013567, and C45678R, as illustrated in Fig 2. To transit or move from the fifth gear ratio to the sixth gear ratio, the clutch CB12345R is disengaged and the clutch C23468 is engaged.

Referring to the seventh gear ratio, this is achieved by en- gaging the clutches CB127BR, 013567, and C45678R, as illus-trated in Fig 2. To transit or move from the sixth gear ratio to the seventh gear ratio, the clutch C23468 is disengaged and the clutch CB1278R is engaged.

Referring to the eighth gear ratio, this is achieved by engag-ing the clutches CB1278R, 023468, and C45678R, as illustrated -11 -in Fig 2. To transit or move from the seventh gear ratio to the eighth gear ratio, the clutch C13567 is disengaged and the clutch C23468 is engaged.

In summary, just engagement of four of the clutches 013567, 023468, C45678R, 0B1278R, and CB12345R is sufficient to pro-vide the hill hold gear ratio whilst engagement of three of the clutches 013567, 023468, 045678R, 0B1278R, and 0B12345R is sufficient to provide the forward or reverse gear ratios. In addition, the transmission 10 can shift directly from the first, the second, or the third gear ratio to the hill-hold gear ratio by just one additional clutch engagement.

Fig. 4 shows a stick diagram of an embodiment of a second transmission 10' . The second transmission 10' and the first transmission 10 have similar parts. The similar parts of the second transmission 10' are named with a prime symbol.

The second transmission 10' differs from the first transmis-sion 10 in connections of one clutch C45678R.

The second transmission 10' includes an input shaft 12' and an output shaft 13', both of which lies in a same longitudinal axis.

A plurality of gear sets is positioned between the input shaft 12' and the output shaft 13' . The gear sets are connected to the input shaft 12 and to the output shaft 13. The gear sets includes a first gear set 15', a second gear set 16', a third gear set 17', and a fourth gear set 18' . The input shaft 12', the output shaft 13', and the gear sets 15', 16', 17', and 18' are located in a casing 20' Positionally, the first gear set 15' is provided next to the second gear set 16' that is provided next to the third gear -12 -set 17' The third gear set 17' is provided next to the fourth gear set 18' In particular, the first gear set 16' includes a plurality of first planetary gears that meshes with a first ring gear Ri' and with a first sun gear Si' The first planetary gears are jointed to a first planetary carrier PCi' In a similar manner, the second gear set 17' includes a plu-rality of second planetary gears that meshes with a second ring gear R2' and with a second sun gear S2'. The second planetary gears are jointed to a second planetary carrier P02' The third gear set 18' includes a plurality of third planetary gears that meshes with a third ring gear R3' and with a third sun gear S3' The third planetary gears are jointed to a third planetary carrier P03' The fourth gear set 19' includes a plurality of fourth plane-tary gears that meshes with a fourth ring gear R4' and with a fourth sun gear S4' The fourth planetary gears are jointed to a fourth planetary carrier P04' Referring to the first gear set 15', the first planetary car-rier PCi' is fixed to the fourth ring gear R4' . The first ring gear Ri' is selectively fixed to the casing 20' via a clutch CB12345R' . The first sun gear 1' is selectively fixed to the casing 20 via a clutch CB1278R' and it is fixed to the second sun gear S2' Referring to the second gear set 16', the second planetary carrier P02' is fixed to the input shaft 12' and it is selec-tively fixed to the fourth sun gear S4' via a clutch 013567' The second ring gear R2' is fixed to the third sun gear S3' -13 -and it is selectively fixed to the fourth sun gear S4' via a clutch C23468' Referring to the third gear set 17', the third planetary car-rier PC3' is selectively fixed to the fourth planetary carrier PC4' via a clutch C45678R' . The third ring gear R3' is fixed to the fourth sun gear S4' and it is selectively fixed to the third sun gear S3' via the clutch C23468' . The third sun gear S3' is selectively fixed to the fourth sun gear S4' via the clutch C23468' Referring to the fourth gear set 18', the fourth planetary carrier PC4 is fixed to the output shaft 13.

Comparing the second transmission 10' with the first transmis-sion 10, the clutch C45678R of the transmission 10 selectively provides a link between the fourth sun gear S4 and the third ring gear R3 whilst a clutch C45678R' of the second transmis-sion 10' selectively provides a link between a third planetary carrier PC3' and a fourth planetary carrier PC4' Fig. 5 shows a table of friction elements of the second trans-mission 10' that is similar to the friction element table of the first transmission 10. The friction elements table of the second transmission 10' shows a hill hold gear ratio, one re-verse gear ratio, and eight forward gear ratios.

The hill hold gear ratio is achieved by engaging the clutches C31278R', C312345R', C23468', and C45678R', as illustrated in Fig 5. This hill hold gear ratio has a torque flow that is the same or similar to the hill-hold torque flow of Fig. 3. The torque flow locks or fixes the output shaft 13' to the casing 20', which thereby prevents the output shaft 13' from turning to provide the hill hold function.

-14 -This hill hold gear ratio has an advantage of not requiring hardware modification or upgrade for its implementation. Only a simple application of the appropriate clutches is needed.

Although the above description contains much specificity, these should not be construed as limiting the scope of the em-bodiments but merely providing illustration of the foreseeable embodiments. Especially the above stated advantages of the em-bodirnents should not be construed as limiting the scope of the embodiments but merely to explain possible achievements if the described embodiments are put into practise. Thus, the scope of the embodiments should be determined by the claims, rather than by the examples given.

-15 -Reference Number first transmission 12 input shaft 13 output shaft first gear set 16 second gear set 17 third gear set 18 fourth gear set 20 casing 10' second transmission 12' input shaft 13' output shaft 15' first gear set 16' second gear set 17' third gear set 18' fourth gear set 20' casing Ri first ring gear Si first sun gear PCi first planetary carrier R2 second ring gear S2 second sun gear PC2 second planetary carrier R3 third ring gear S3 third sun gear PC3 third planetary carrier R4 fourth ring gear S4 fourth sun gear PC4 fourth planetary carrier CB12345R clutch C31278R clutch C13567 clutch -16 -C23468 clutch C45678R clutch Ri' first ring gear Si' first sun gear PCi' first planetary carrier R2' second ring gear S2' second sun gear PC2' second planetary carrier R3' third ring gear S3' third sun gear PC3' third planetary carrier R4' fourth ring gear S4' fourth sun gear PC4' fourth planetary carrier CB12345R' clutch CB1278R' clutch C13567' clutch C23468' clutch C45678R' clutch