GB2309756A

GB2309756A - Four speed automatic transmission allows ratio change by the operation of a single clutch

Info

Publication number: GB2309756A
Application number: GB9602273A
Authority: GB
Inventors: Roland Mathis
Original assignee: Delphi Automotive Systems France
Current assignee: Delphi Automotive Systems France
Priority date: 1996-02-05
Filing date: 1996-02-05
Publication date: 1997-08-06
Anticipated expiration: 2016-02-05
Also published as: GB9602273D0; GB2309756B

Abstract

An automatic transmission (10) comprising; a planetary gear train (14) mounted within the housing; an input drive shaft (16) for providing input drive to the planetary gear train; an output drive shaft (18) connected with an output drive (32) from the planetary gear train; a first brake (C1) acting on a first reaction input (26) to the planetary gear train; a second brake (C2) acting on a second reaction input (28) to the planetary gear train and the housing; a third clutch (C3) connected between a first drive input (22) to the planetary gear train and the input drive shaft; and a fourth clutch (C4) connected between a second drive input (24) to the planetary gear train and the input drive shaft; wherein for first forward gear ratio the first brake is engaged; for second forward gear ratio the first and second brakes are engaged; for third forward gear ratio the first and second brakes and the third clutch are engaged; and for fourth forward gear ratio the first and second brakes and the third and fourth clutches are engaged. Allows gear shift by the operation of a single clutch.

Description

AUTOMATIC TRANSMISSION The present invention relates to an automatic transmission having four or more forward speed ratios.

Automatic transmissions are known in which the operation of a planetary gear train is controlled to provide the desired output gear ratio. In these known arrangements, a number of friction devices, that is, clutches and brakes, are engaged and disengaged to control the relative rotation of the gears of the planetary gear train to provide the required gear ratio.

A problem with known arrangements is the necessity to control the timing of the disengagement of a clutch or brake whilst substantially simultaneously engaging another clutch or brake to provide a change from one gear ratio to another gear ratio.

It is an object of the present invention to overcome this problem.

An automatic transmission in accordance with the present invention comprises a housing; a planetary gear train mounted within the housing; an input drive shaft for providing input drive to the planetary gear train; an output drive shaft connected with an output drive from the planetary gear train; a first clutch connected between the housing and a first reaction input to the planetary gear train; a second clutch connected between a second reaction input to the planetary gear train and the housing; a third clutch connected between a first drive input to the planetary gear train and the input drive shaft; and a fourth clutch connected between a second drive input to the planetary gear train and the input drive shaft; wherein for first forward gear ratio the first clutch is engaged; for second forward gear ratio the first and second clutches are engaged; for third forward gear ratio the first, second and third clutches are engaged; and for fourth forward gear ratio the first, second, third and fourth clutches are engaged.

In the present invention, therefore, a gear change or shift between adjacent forward ratios is achieved by the engagement or disengagement of a single clutch, thereby eliminating the need for a timed engagement and disengagement of two or more friction elements.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a first embodiment of automatic transmission in accordance with the present invention; Figure 2 is a schematic diagram of a second embodiment of automatic transmission in accordance with the present invention; and Figure 3 is a table of gear ratio and clutch engagement for the automatic transmission of Figure 1 or Figure 2.

Referring to Figure 1, a first embodiment of automatic transmission 10 in accordance with the present invention is shown. The transmission 10 is capable of providing five forward speed ratios and one reverse speed ratio. The automatic transmission 10 comprises a housing 12, a planetary gear train 14, an input drive shaft 16 and an output drive shaft 18. The input drive shaft 16 is connectable with the output drive shaft of an engine or other powered driving means (not shown), preferably by way of a torque converter (not shown), in any suitable manner known to those skilled in the art. The output drive shaft 18 is connected to the driven wheels (not shown) of a motor vehicle or other rotatably driven means by way of an output drive wheel 20.The planetary gear train 14 comprises a pair of planetary gear sets 40,42 each comprising a sun gear 44,46, respectively, and a ring gear 48,50, respectively. The first planetary gear set 40 further comprises first and second pinion gears 52,54, respectively, interengaging the sun gear 44 and the ring gear 48, the pinion gears being rotatably mounted on a common planet carrier 56. The pinion gear 52 is a short pinion which engages the sun gear 44 and the pinion gear 54. The pinion gear 54 is a long pinion which engages the pinion gear 52 and the ring gear 48.

The second planetary gear set 42 further comprises the long pinion gear 54 and a pinion gear 58, the pinion gears being rotatably mounted on a common planet carrier 60 which is connected with the planet carrier 56. The pinion gear 58 is a short pinion which engages the ring gear 50 and the pinion gear 54. The pinion gear 54 engages the pinion gear 58 and the sun gear 46. The sun gears 44,46 and the ring gears 48,50 have a common centre line R (axis of rotation) which is substantially parallel to the centre lines L, L1, L2 (rotational axes) of the pinion gears 52,54,58. The planet carrier 60 of the second planetary gear set 42 drives the output drive shaft 18 and the output drive wheel 20. Additional identical sets of pinion gears 52,54,58 may be positioned between the sun gears 44,46 and the ring gears 48,50.

Alternatively, where there are two or more long pinion gears 54, a reduced number of short pinion gears 52,58 may be used.

The planetary gear train 14 has first and second drive inputs 22,24, respectively, connectable with the input drive shaft 16. The planetary gear train 14 also has first, second, third and fourth reaction inputs 26,28,30,32, respectively, connectable with the housing 12. The first drive input 22 is connected with the ring gear 50 of the second planetary gear set 42. The second drive input 24 is connected with the sun gear 46 of the second planetary gear set 42. The first reaction input 26 is connected with the ring gear 48 of the first planetary gear set 40. The second reaction input 28 is connected with the sun gear 44 of the first planetary gear set 40. The third reaction input 30 is connected with the sun gear 46 of the second planetary gear set 42.

The fourth reaction input 32 is connected with the ring gear 50 of the second planetary gear set 42. The first reaction input 26 is connectable with the housing 12 by way of a first clutch C1 and a first free wheel or oneway coupling F1. The second reaction input 28 is connectable with the housing 12 by way of a second clutch C2 and a second free wheel or one-way coupling F2. The first drive input 22 is connectable with the input drive shaft 16 by way of a third clutch C3. The second drive input 24 is connectable with the input drive shaft 16 by way of a fourth clutch C4 and a third free wheel or one-way coupling F3. The third reaction input 30 is connectable with the housing 12 by way of a fifth clutch CS.A sixth clutch C6 and a fourth free wheel or one-way coupling F4 are connected in parallel with the fourth clutch C4 and third one-way coupling F3 between the second drive input 24 and the input drive shaft 16. The fourth reaction input 32 is connectable with the housing 12 by way of a seventh clutch C7.

Referring to Figure 3, the automatic transmission 10 is capable of providing a first forward gear ratio, a second forward gear ratio which is less than the first ratio, a third forward gear ratio which is less than the second ratio, a fourth forward gear ratio which is less than the third ratio, a fifth forward gear ratio which is less than the fourth forward gear ratio, and a reverse gear ratio. Preferably, the fourth ratio is direct drive, and the fifth ratio is an overdrive.

For first forward gear ratio operation, first and sixth clutches C1 and C6 are engaged (applied) and first and fourth one-way couplings F1 and F4 are also engaged (under load). The other clutches remain disengaged and the other one-way couplings act as an over-running free wheel. For second forward gear ratio operation, first, second, and sixth clutches C1, C2 and C6 are engaged and fourth one-way couplings F4 is also engaged. For third forward gear ratio operation, first, second, third and sixth clutches C1, C2, C3 and C6 are engaged and second one-way coupling F2 is also engaged.

For fourth forward gear ratio operation, first, second, third, fourth and sixth clutches C1, C2, C3, C4 and C6 are engaged and third one-way coupling F3 is engaged.

For fifth forward gear ratio operation, first, second, third, fourth and fifth clutches C1, C2, C3, C4 and C5 are engaged. For reverse gear ratio, sixth and seventh clutches C6 and C7 are engaged and fourth one-way coupling F4 is engaged.

The shift from fourth forward gear ratio to fifth forward gear ratio is achieved by engaging (applying) fifth clutch CS and disengaging (releasing) sixth clutch C6. However, sixth clutch C6 can be released/applied approximately one second before/after fifth clutch C5 is applied and so there is no need for complex time control of the operation of these clutches C5, C6.

It will be appreciated, therefore, that a shift from first forward gear ratio to second forward gear ratio is achieved by engaging (applying) second clutch C2. Similarly, a shift from second forward gear ratio to third forward gear ratio is achieved by engaging (applying) third clutch C3, a shift from third forward gear ratio to fourth forward gear ratio is achieved by engaging (applying) fourth clutch C4, and a shift from fourth forward gear ratio to fifth forward gear ratio is achieved by engaging (applying) fifth clutch C5. All of these shifts can be achieved without the need for complex time control of the operation of the clutches.

The ratios of the five forward gears may be calculated as shown in Figure 3. In these calculations, the number of teeth on the long pinion gear 54 is taken to be the same for each planetary gear set 40,42. Also, in these calculations, dl is the number of teeth on the ring gear 48 of the first planetary gear set 40, al is the number of teeth on the sun gear 44 of the first planetary gear set 40, d2 is the number of teeth on the ring gear 50 of the second planetary gear set 42, and a2 is the number of teeth on the sun gear 46 of the second planetary gear set 42. It will be appreciated that where the number of teeth at each end of the long pinion gear 54 is different, than alternative calculations will be required.

In the second embodiment of automatic transmission 100 shown in Figure 2, the relative positions of the short pinion gear 52' and long pinion gear 54' in the first planetary gear set 40' have been reversed, and similarly the relative positions of the short pinion gear 58' and long pinion gear 54' in the second planetary gear set 42' have also been reversed.

In this arrangement, the drive to the output drive shaft 18 is taken from the planet carrier 56 of the first planetary gear set 40'. All other features of this automatic transmission 100 are the same as the automatic transmission 10 of Figure 1, and like parts have been given the same reference number. The details given with respect to Figure 3 also apply to this second embodiment of automatic transmission 100.

In the present invention, shifts from one ratio to another can be achieved solely by operating only one clutch, removing the need for timing control of engaging/disengaging clutches, thereby providing quieter and more reliable gear shifts.

The present invention may be used with other layouts for the planetary gear train. The automatic transmission of the present invention is primarily intended for use in a motor vehicle. The present invention has particular application in a motor vehicle having front wheel drive.

Claims

Claims:

1. An automatic transmission comprising a housing; a planetary gear train mounted within the housing; an input drive shaft for providing input drive to the planetary gear train; an output drive shaft connected with an output drive from the planetary gear train; a first clutch connected between the housing and a first reaction input to the planetary gear train; a second clutch connected between a second reaction input to the planetary gear train and the housing; a third clutch connected between a first drive input to the planetary gear train and the input drive shaft; and a fourth clutch connected between a second drive input to the planetary gear train and the input drive shaft; wherein for first forward gear ratio the first clutch is engaged; for second forward gear ratio the first and second clutches are engaged; for third forward gear ratio the first, second and third clutches are engaged; and for fourth forward gear ratio the first, second, third, fourth and fifth clutches are engaged.

2. An automatic transmission as claimed in Claim 1, further comprising a fifth clutch connected between a third reaction input and the housing, wherein for fifth forward gear ratio the first, second, third, fourth and fifth clutches are engaged.

3. An automatic transmission as claimed in Claim 1 or Claim 2, wherein the planetary gear train comprises first and second planetary gear sets; the first planetary gear set comprising a sun gear, a ring gear, first and second pinion gears, and a planet carrier on which the first and second pinion gears are rotatably mounted, the first pinion gear engaging the sun gear and the second pinion gear and the second pinion gear engaging the ring gear and the first pinion gear; the second planetary gear set comprising a sun gear, a ring gear, first and second pinion gears, and a planet carrier on which the first and second pinion gears are rotatably mounted, the first pinion gear engaging the sun gear and the second pinion gear and the second pinion gear engaging the ring gear and the first pinion gear; wherein the planet carriers of the first and second planetary gear sets are connected together; wherein one of the first or second pinion gears of the first planetary gear set is connected with one of the first or second pinion gears of the second planetary gear set to form a long pinion gear; and wherein the first drive input is connected to the ring gear of the second planetary gear set; the second drive input is connected to the sun gear of the second planetary gear set; the first reaction input is connected to the ring gear of the first planetary gear; and the second reaction input is connected to the ring gear of the first planetary gear set.

4. An automatic transmission as claimed in Claim 3, wherein the long pinion gear engages the ring gear of the first planetary gear set and the sun gear of the second planetary gear set; and wherein the planet carrier of the second planetary gear set is connected to the output drive shaft.

5. An automatic transmission as claimed in Claim 3, wherein the long pinion gear engages the ring gear of the second planetary gear set and the sun gear of the first planetary gear set; and wherein the planet carrier of the first planetary gear set is connected to the output drive shaft.

6. An automatic transmission as claimed in any one of Claims 3 to 5 comprising a fifth clutch as claimed in Claim 2, wherein the third reaction input is connected to the sun gear of the second planetary gear set.

7. An automatic transmission substantially as herein described with reference to, and as shown in, the accompanying drawings.