GB2309757A

GB2309757A - Four speed automatic transmission allows ratio change by the operation of a single clutch

Info

Publication number: GB2309757A
Application number: GB9602279A
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: GB2309757B; GB9602279D0

Abstract

An automatic transmission (10) comprises 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 clutch (C1) connected between the input drive shaft and a first drive input (22) to the planetary gear train; a second brake (C2) connected acting on a first reaction input (28) to the planetary gear train; a third brake (C3) acting on a second drive input (24) to the planetary gear train; and a fourth clutch (C4) connected between the input drive shaft and a third drive input (26) to the planetary gear train; wherein for first forward gear ratio the first clutch is engaged; for second forward gear ratio the first clutch and the second brake are engaged; for third forward gear ratio the first clutch and the second and third brakes are engaged; and for fourth forward gear ratio the first, second 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 input drive shaft and a first drive input to the planetary gear train; a second clutch connected between a first reaction input to the planetary gear train and the housing; a third clutch connected between a second drive input to the planetary gear train and the housing; and a fourth clutch connected between the input drive shaft and a third drive input to the planetary gear train; 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 an automatic transmission in accordance with the present invention; and Figure 2 is a table of gear ratio and clutch engagement for the automatic transmission of Figure 1.

Referring to Figure 1, an 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) by way of a torque converter 20 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 in any suitable manner known to those skilled in the art. The planetary gear train 14 may be any suitable arrangement of planetary gears.

The planetary gear train 14 has first, second and third drive inputs 22,24,26, respectively, connectable with the input drive shaft 16. The planetary gear train 14 also has first and second reaction inputs 28,30, respectively, connectable with the housing 12, and an output drive 32 connected with the output drive shaft 18. The first drive input 22 is connectable with the input drive shaft 16 by way of a first clutch C1 and a first free wheel or one-way coupling FW1. The first 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 FW2. The second drive input 24 is connectable with the housing by way of a third clutch C3 and a third free wheel or one-way coupling FW3. The third drive input 26 is connectable with the input drive shaft 16 by way of a fourth clutch C4.The second drive input 24 is also connectable with the housing by way of a fifth clutch C5. A sixth clutch C6 is connected in parallel with the first clutch C1 and one-way coupling FW1 between the first drive input 22 and the input drive shaft 16. The second reaction input 30 is connectable with the housing by way of a fourth free wheel or one-way coupling FW4 and by way of a seventh clutch C7. An eighth clutch C8 is connected in parallel with the second clutch C2 and one-way coupling FW2 between the second reaction input 28 and the housing 12. A ninth clutch C9 is connected between the second drive input 24 and the input drive shaft 16.

Referring to Figure 2, 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 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, sixth and seventh clutches C1, C6 and C7 are engaged (applied) and first and fourth one-way couplings FW1 and FW4 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, sixth and eighth clutches C1, C2, C6 and C8 are engaged and first and second one-way couplings FWl and FW2 are also engaged.

For third forward gear ratio operation, first, second, third, fifth and sixth clutches C1, C2, C3, C5 and C6 are engaged and first and third one-way couplings FW1 and FW3 are also engaged. For fourth forward gear ratio operation, first, second, third, fourth and sixth clutches C1, C2, C3, C4, and C6 are engaged and first one-way coupling FWl is also engaged. For fifth forward gear ratio operation, first, second, third, fourth and fifth clutches C1, C2, C3, C4 and CS are engaged. For reverse gear ratio, seventh and ninth clutches C7 and C9 are engaged.

In first forward gear ratio, sixth and seventh clutches C6 and C7 are applied to overrun the first and fourth one-way couplings FW1 and FW4 in order to provide engine braking. This means the application of these clutches C6, C7 can be delayed as they do not participate in a shift to or from first forward gear ratio. Similarly, in second forward gear ratio, sixth and eighth clutches C6 and C8 are applied to overrun the first and second one-way couplings FW1 and FW2 in order to provide engine braking. This means the application of these clutches C6, C8 can be delayed as they do not participate in a shift to or from second forward gear ratio. Further, in third forward gear ratio, fifth and sixth clutches CS and C6 are applied to overrun the first and third one-way couplings FW1 and FW3 in order to provide engine braking. This means the application of these clutches C5, C6 can be delayed as they do not participate in a shift to or from third forward gear ratio. Finally, in fourth forward gear ratio, sixth clutch C6 is applied to overrun the first one-way coupling FW1 in order to provide engine braking. This means the application of this clutch C6 can be delayed as it does not participate in a shift to or from fourth forward gear ratio. The shift from fourth forward gear ratio to fifth forward gear ratio is achieved by engaging (applying) fifth clutch C5 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.

During these gear ratios the following kinematic conditions are satisfied by the planetary gear train 14. In first forward gear ratio, the effective rotational speed on the first reaction input 28 must be less than zero. In second forward gear ratio, the effective rotational speed of the second drive input 24 must be less than zero, the effective rotational speed on the first reaction input 28 must be greater than zero, and the effective rotational speed on the second reaction input 30 must be greater than zero. In third forward gear ratio, the effective rotational speed of the second drive input 24 is zero, the effective rotational speed on the first reaction input 28 must be greater than zero, and the effective rotational speed on the second reaction input 30 must be also greater than zero.In fourth forward gear ratio, the torque acting on the first drive input 22 is positive to allow for the delayed release of the clutch C6. In fifth forward gear ratio, the effective rotational speed of the second drive input 24 is zero, the effective rotational speed on the first reaction input 28 must be greater than zero, the effective rotational speed on the first drive input 22 is greater than the effective rotational speed on the input drive shaft 16, and the effective rotational speed of the second reaction input must be greater than zero. In reverse gear ratio, no kinematic conditions apply as all the clutches are in a released state except for seventh and ninth clutches C7 and C9.

These conditions help to ensure that 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 planetary gear train 14 may be any suitable arrangement which provides the above mentioned kinematic conditions, but preferably comprises a pair of planetary gear sets each comprising a sun gear, a ring gear, and a number of pinion gears interengaging the sun gear and the ring gear, the pinion gears being rotatably mounted on a planet carrier. The automatic transmission of the present invention is primarily intended for use in a motor vehicle.

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 input drive shaft and a first drive input to the planetary gear train; a second clutch connected between a first reaction input to the planetary gear train and the housing; a third clutch connected between a second drive input to the planetary gear train and the housing; and a fourth clutch connected between the input drive shaft and a third drive input to the planetary gear train; 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.

2. An automatic transmission as claimed in Claim 1, further comprising a fifth clutch connected between the second drive 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, further comprising additional clutches and one-way couplings, the additional clutches being engageable to overrun any engaged one-way coupling to provide braking to the planetary gear train from an engine when driving the input drive shaft.

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