GB2111651A

GB2111651A - Hydrodynamic drive coupling

Info

Publication number: GB2111651A
Application number: GB08137012A
Authority: GB
Inventors: Claude Peter Windsor-Smith; Raymond Alfred Tailby
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-12-08
Filing date: 1981-12-08
Publication date: 1983-07-06
Also published as: BR8208079A

Abstract

A drive coupling (10) suitable for coupling a turbo-charged diesel engine to a constant mesh change speed gear train comprises drive input and drive output members (20, 24) having blades (22, 26) and similar in form to the corresponding parts of a conventional fluid coupling. A reactor member (28) is provided between the drive input and drive output members and has blades arranged to provide torque multiplication of from 1.6 to 2.2 at stall, and preferably in the range of 1.7 to 1.9 whereby the drive coupling provides sufficient torque multiplication to offset the torque decreasing effect of the turbocharger at low engine speeds, while retaining the coupling efficiency of a fluid coupling at normal road speeds and nevertheless avoiding the need for oil pumps and coolers as required by torque converters. <IMAGE>

Description

SPECIFICATION Drive coupling This invention relates to drive couplings, and in particular, though not exclusively, to drive couplings for transmitting drive from a vehicle engine to a change speed gear train from which drive is transmitted onwards to the wheels of the vehicle.

The invention is particularly applicable to couplings for use in highway or road vehicles particularly heavy duty vehicles such as lorries or trucks, but is also applicable to other vehicles such as railway locomotives, and indeed to any other drive transmission in which characteristics comparable to those discussed below are desirable.

The invention also provides the combination of a coupling with a gear train and other components of a drive transmission, and the combination of the coupling with a prime mover, engine or power plant, particularly a supercharged orturbocharged internal combustion engine.

In the case of drive transmissions for highway vehicles various types of drive couplings have been employed to transmit drive between the engine and the gearbox of the vehicle. These include various types of friction clutch, and electrical and hydraulic devices. These couplings are in many cases used to take up the drive when the vehicle moves off from rest, but by no means is this always a requirement and the present invention is not limited by this function.

In the case of hydraulic and fluid coupling devices, the two main types which have been provided are the so-called "fluid couplings" as such, and "torque converters".

In fluid couplings, the bladed impellor is driven by the engine and rotates within a fluid-filled bladed housing coupled to the output shaft. The drive coupling slips readily for drive takeup purposes, but becomes a solid coupling at about 800 to 900 revolutions per minute.

In the case of torque converters, an annular set of reactor blades is provided in the housing between the drive input impellor blades and the drive output turbine blades so as to modify the torque characteristics of the coupling and provide greatly increased torque transmission (as compared with a fluid coupling) under drive take-up conditions.

The principal disadvantage of plain fluid couplings is that they provide no torque multiplication for drive take-up. Nevertheless, they are relatively simple and transmit drive efficiently at all normal road speeds.

Torque converters however, though providing useful torque multiplication are relatively complex and expensive, involving the use of oil pumps and oil coolers due to heat generated in the torque converter. Moreover, they are relatively inefficient at normal road speeds, involving a loss of about 20% of their power input (as compared with 5% for fluid couplings) Attempts have been made to improve the efficiency of torque converters, including proposals for lock-up clutches which change the torque converter at medium roads speeds and above into a simple mechanical coupling. However, such lock-up clutches are relatively complex and expensive.

A further factor in relation to torque converters is that they provide excessive torque during drive take-up and measures have to be taken to avoid over stressing the other components of the vehicle transmission.

The usual arrangement of a torque converter in a vehicle transmission is in combination with a planetary or epicyclic gearbox, with the drive output from the reactor transmitted directly to the planetary carrier of the first epicyclic gear train. Although this combination is satisfactory for cars and buses which have a relatively favourable power to weight ratio, it is not well suited to lorries and trucks which have a much less favourable power to weight ratio. This is because the maximum number of transmission ratios obtainable from an epicyclic gearbox of reasonable dimensions is five whereas lorries and trucks usually need at least six and often more transmission ratios.This situation is aggravated where the lorry or truck has a supercharged or turbocharged engine, due to the fact that the engine, though generally more efficient has to be modified in ways which reduce its available torque output at low engine speeds, and thus such an engine may well require one or two additional transmission ratios.

An object of the present invention is to provide a drive coupling and a drive coupling in combination with a change speed gear train and/or a power plant or engine, offering improvements in relation to one or more of the technical problems identified above.

According to the invention there is provided a drive coupling. The drive coupling comprises a drive input member having blades and adapted to be connected to a drive input shaft, and a drive output member having blades and adapted to be connected to a drive output shaft, the assembly being capable of functioning in the manner of a fluid coupling at rates of rotation above a predetermined rate. The coupling is also provided with a reactor member having blades and positioned in the flow path of fluid moving between said drive output member and said drive input member. The reactor member may be mounted so as to be non-rotatable or grounded for example by being connected to the housing of a gear train connected to the drive output shaft of the coupling.Alternatively, the reactor member may be supported on a freewheel mounting so as to modify the operating characteristics of the coupling. The freewheel mounting grounds the reactor member at low rotational speeds of the coupling and at higher rotational speeds the reactor member can rotate in the drive direction. The freewheel mounting may itself be mounted on a non-rotatable structure whereby the torque output of the reactor member is not transmitted to the drive train. The reactor member is preferably constructed so as to modify The drawing originally filed was informal and the print here reproduced is taken from a laterfiledformal copy.

the torque transmission characteristics of the drive coupling so as to provide, at stall, torque multiplication of from 1.6 to 2.2 and preferably from 1.7 to 1.9.

These values of torque multiplication can be achieved by suitable choice of reactor blade angles, length and profiles.

In the case where the reactor member is grounded and non-rotatable, it may be mounted on a sleeve secured to a non-rotatable structure, such as the housing of a gearbox to which the drive coupling transmits torque. The sleeve may be mounted in concentric relation with a drive output shaft of the drive coupling to which said drive output member is connected. Where the reactor member is supported on a freewheel mounting, the latter may itself be mounted on said non-rotatable sleeve.

The invention also provides a drive transmission comprising the drive coupling as defined in the preceding paragraphs in combination with a change speed gear train. The train may be of any desired construction, but a gear train as disclosed in our co-pending application entitled "Gear Trains" is particularly suitable and we hereby incorporate in the present application the entire disclosure of said co-pending application and of our prior pending UK applications 7847198 (published as GB 2,036,892 A) and 7847138 (published as GB 2,036,891 A) and 81 13649 (to be published as GB 2,076;910 A).These latter applications all relate to gear trains having clutch-controlled layshaft gears in constant mesh with drive input and drive output gears and capable of providing any desired number of transmission ratios. Reference is particularly directed to our application filed herewith entitled "Gear Trains" which discloses a modification of such gear trains by the addition of a "range layshaft" providing high and low ratio versions of each layshaft transmission ratio thereby doubling the number of available ratios and enabling a two layshaft gear train to provide a total of six transmission ratios.

The invention also provides the combination of the above drive coupling and geartrain with a supercharged (particularly a turbocharged) internal combustion engine such as a diesel engine.

In an embodiment of the invention described below, the provision of a reactor member grounded on a non-rotatable structure and arranged so that the drive coupling provides only modest torque multiplication, the advantage is provided of a coupling providing the necessary torque multiplication for drive take-up purposes, particularly on heavy duty vehicles such as lorries, without the efficiency penalties of conventional torque converters. The coupling functions, at normal road speed, as a conventional fluid coupling providing around 95% coupling efficiency. Moreover, this is achieved without the use of a lock-up clutch and due to the modest torque multiplication, oil heating is reduced and for at least some applications the provision of an oil pump and an oil cooler is unnecessary-thereby further improving efficiency.Moreover, the provision of only modest torque multiplication avoids overstressing other drive transmission components.

The combination of the drive coupling described in the embodiment below with a gear train providing six or more transmission ratios, and with a supercharged internal combustion engine, provides a vehicle drive capable of meeting the requirements of heavy duty truck or lorry operations, including providing facilities for hill starts, while retaining the important fuel efficiency of a supercharged engine, and without the offsetting inefficiency of a torque converter, and without the inherent cost complexity of a lock-up clutch.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows an axial section through a drive coupling according to the invention; and Fig. 2 shows graphs of torque-against speed for vehicle drives incorporating turbocharged and unturbocharged engines, with an indication of the effect on the torque characteristics of a turbocharged engine of a conventional torque converter and of a drive coupling according to the present invention.

As shown in Fig. 1, a drive coupling 10 is provided for transmitting drive between an input shaft 12 and an output shaft 14 which are mounted end to end with coupling 10 encircling them, for rotation about a common axis 15. Output shaft 14 is received in a bearing 16 of a gearbox 18 to which it transmits drive.

Thus drive coupling 10 forms the drive input device for gearbox 18. The gearbox may be of any convenient form but preferably is of the kind described in our co-pending and prior co-pending UK patent applications mentioned above, and comprising layshafts having layshaft gears meshing with input and output gears of a central gearbox shaft means, each layshaft having an end clutch for selective transmission of drive through the layshaft between the central drive input and drive output gears of the gearbox.

Drive coupling 10 comprises a drive input member 20 having blades 22 for engagement with a drive transmission fluid (not shown) which fills the drive coupling, and a drive output member 24 having corresponding blades 26 to receive drive from the drive input member through the fluid. A reactor member 28 of annular form and having blades 30 to co-operate with the same fluid, is provided between the drive input and output members 20 and 24.

Drive input member 20 and drive output member 24, and their blades 22,26 are similar in form to the corresponding parts of a conventional fluid coupling. Drive input member 20 is in the form of an annular housing which is split circumferentially into housing portions 32,34 secured together by bolts 36.

The drive input blades 22 are secured to housing portion 34, and housing portion 32 is recessed to receive an annular channel section portion 38 of output member 24, on which the output blades 26 are mounted.

Input and output members 20 and 24 are rigidly secured to their corresponding input and output shafts 12 and 14 respectively so as to be non-rotatable with respect thereto. The axially inner side 40 of input member 20 is bored-outto receive a non-rotatable collar 42.

The collar is secured by bolts 44 to gearbox 18. A seal 46 prevents leakage of hydraulic power trans mission fluid between inner end 40 of drive input member 20 which rotates during use, and the stationary collar 42.

Reactor member 28 is annular in form and co-ax ially mounted with shafts 12 and 14 and comprises a mounting collar 48 carrying the fluid reactor blades 30 which extend outwardly therefrom between the radially inner ends of input and output blades 22 and 26.

The reactor member mounting collar 48 is secured to main collar 42 so as to be non-rotatable with respect thereto, and thus the entire reactor member is grounded and non-rotatable.

The attitudes, length and profiles of the blades 30 of reactor member 28 are such that the reactor member provides torque multiplication of from 1.6 to 2.2 at stall between the drive input and the drive output members 20 and 24. The preferred range of torque multiplication is from 1.7 to 1.9. A particular feature of significance in relation to the torque multiplication achieved is the exit angle for each reactor blade. In order to achieve the very modest torque multiplication provided by the drive coupling of the present invention a relatively large exit angle is appropriate.

The structure of the reactor member may be varied somewhat while achieving the necessary torque multiplication as identified above and, for example, the reactor member may be provided with a hub mounting for the blades, the hub being machined from a forging and being formed with slots to receive the blade ends, the blades being made from lengths of strip stock, rolled to the appropriate shape.

In use, input shaft 12 is provided by the drive output shaft of a supercharged (preferably turbocharged) diesel engine, and gearbox 18 is of the constant mesh multi-layshaft kind identified above, preferably providing six or more drive transmission ratios. The drive output from gearbox 18 proceeds via propeller shafts and a differential drive unit to ground wheels of the road vehicle.

At tickover engine speed very little drive is trans mittedthrough coupling 10 and even if a drive transmission ratio in gearbox 18 is engaged the vehicle can be easily held on the hand brake. On increasing engine speed, drive begins to be trans mittedthrough coupling 10 and reactor member 28 provides, initially, torque multiplication of, say, 1.75 to 1. As a result, in the case of a transmission for a heavy torry or truck, the lowest ratio of gearbox 18 can provide more torque than with a conventional fluid coupling or a simple clutch, thereby assisting hill starts underfull load, and other heavy duty conditions.

As the speed of the vehicle increases and the rate of rotation of the output member 24 and its blade 26 correspondingly the increases, the torque ratio or multiplication provided by the coupling decreases until it reaches zero at the "coupling point". Thereafter, the drive coupling 10 functions in the same way as a conventional fluid coupling with minimal energy loss.

It is noteworthy that in the above embodiment no oil pump and external oil cooler is provided or required due to the low torque multiplication and the fact that housing portions 32,34 can dissipate the heat generated adequately. This represents a signifi cant energy saving feature.

Referring to Fig 2, curves 50 and 52 show the torque available from a diesel engine in ordinary and turbocharged form respectively, as engine speed (rate of rotation) varies. It is noteworthy that the torque available from the turbocharged engine falls to a level below that of its unturbocharged counterpart at low engine speeds. The consequence of this is that turbocharged engines though relatively fuel-efficient, can have load take-up problems in heavy duty conditions unless provided with an adequate range of transmission ratios and torque multiplication, as in the present embodiment.

Dotted curves 54 and 56 show the effect on the torque availability of the turbocharged engine, of drive coupling 10 and of a conventional torque converter, respectively. The conventional torque converter provides excessive start-up torque which can lead to over stressing of transmission components, whereas coupling 10 provides the necessary offset for the consequences of turbocharging the engine, without any corresponding over stressing problems.

In a further embodiment of the invention, not illustrated, the reator member 28 is supported on a freewheel mounting which is itself directly mounted on main collar 42. Other constructional details of this embodiment remain substantially the same. In use, this embodiment has modified operational characteristics in that the reactor member is effectively grounded and non-rotatable at low rates of rotation of the coupling, but as the rate of rotation of the coupling increases the reator member can begin to rotate in the forward drive direction.

CLAIMS (Filed on 8.12.82) 1. A drive coupling comprising a rotatable drive input member having blades and adapted to be connected to a dirve input shaft, and a drive output member having blades and adapted to be connected to a drive output shaft, the assembly being capable of functioning in the manner of a fluid coupling at rates of rotation above a predetermined rate, and a reactor member have blades and positioned in the flow path of fluid moving between said input and output members, the reactor member being mounted so as to be non - rotatable in the non - drive direction.

2. A coupling according to claim 1 wherein the reactor member is constructed so that the coupling provides, at stall, torque multiplication of from 1.6 to 2.2.

3. A coupling according to claim 2 wherein said torque multiplication is from 1.7 to 1.9.

4. A coupling according to any one of the preceding claims wherein said reactor member is mounted so as to be non - rotatable in both the drive and non - drive directions.

5. A drive coupling according to any one of claims 1 to 4 wherein the reactor member is mounted on a freewheel mounting so as to be rotatable in the drive direction and non - rotatable in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. seal 46 prevents leakage of hydraulic power trans mission fluid between inner end 40 of drive input member 20 which rotates during use, and the stationary collar 42. Reactor member 28 is annular in form and co-ax ially mounted with shafts 12 and 14 and comprises a mounting collar 48 carrying the fluid reactor blades 30 which extend outwardly therefrom between the radially inner ends of input and output blades 22 and 26. The reactor member mounting collar 48 is secured to main collar 42 so as to be non-rotatable with respect thereto, and thus the entire reactor member is grounded and non-rotatable. The attitudes, length and profiles of the blades 30 of reactor member 28 are such that the reactor member provides torque multiplication of from 1.6 to 2.2 at stall between the drive input and the drive output members 20 and 24. The preferred range of torque multiplication is from 1.7 to 1.9. A particular feature of significance in relation to the torque multiplication achieved is the exit angle for each reactor blade. In order to achieve the very modest torque multiplication provided by the drive coupling of the present invention a relatively large exit angle is appropriate. The structure of the reactor member may be varied somewhat while achieving the necessary torque multiplication as identified above and, for example, the reactor member may be provided with a hub mounting for the blades, the hub being machined from a forging and being formed with slots to receive the blade ends, the blades being made from lengths of strip stock, rolled to the appropriate shape. In use, input shaft 12 is provided by the drive output shaft of a supercharged (preferably turbocharged) diesel engine, and gearbox 18 is of the constant mesh multi-layshaft kind identified above, preferably providing six or more drive transmission ratios. The drive output from gearbox 18 proceeds via propeller shafts and a differential drive unit to ground wheels of the road vehicle. At tickover engine speed very little drive is trans mittedthrough coupling 10 and even if a drive transmission ratio in gearbox 18 is engaged the vehicle can be easily held on the hand brake. On increasing engine speed, drive begins to be trans mittedthrough coupling 10 and reactor member 28 provides, initially, torque multiplication of, say, 1.75 to 1. As a result, in the case of a transmission for a heavy torry or truck, the lowest ratio of gearbox 18 can provide more torque than with a conventional fluid coupling or a simple clutch, thereby assisting hill starts underfull load, and other heavy duty conditions. As the speed of the vehicle increases and the rate of rotation of the output member 24 and its blade 26 correspondingly the increases, the torque ratio or multiplication provided by the coupling decreases until it reaches zero at the "coupling point". Thereafter, the drive coupling 10 functions in the same way as a conventional fluid coupling with minimal energy loss. It is noteworthy that in the above embodiment no oil pump and external oil cooler is provided or required due to the low torque multiplication and the fact that housing portions 32,34 can dissipate the heat generated adequately. This represents a signifi cant energy saving feature. Referring to Fig 2, curves 50 and 52 show the torque available from a diesel engine in ordinary and turbocharged form respectively, as engine speed (rate of rotation) varies. It is noteworthy that the torque available from the turbocharged engine falls to a level below that of its unturbocharged counterpart at low engine speeds. The consequence of this is that turbocharged engines though relatively fuel-efficient, can have load take-up problems in heavy duty conditions unless provided with an adequate range of transmission ratios and torque multiplication, as in the present embodiment. Dotted curves 54 and 56 show the effect on the torque availability of the turbocharged engine, of drive coupling 10 and of a conventional torque converter, respectively. The conventional torque converter provides excessive start-up torque which can lead to over stressing of transmission components, whereas coupling 10 provides the necessary offset for the consequences of turbocharging the engine, without any corresponding over stressing problems. In a further embodiment of the invention, not illustrated, the reator member 28 is supported on a freewheel mounting which is itself directly mounted on main collar 42. Other constructional details of this embodiment remain substantially the same. In use, this embodiment has modified operational characteristics in that the reactor member is effectively grounded and non-rotatable at low rates of rotation of the coupling, but as the rate of rotation of the coupling increases the reator member can begin to rotate in the forward drive direction. CLAIMS (Filed on 8.12.82)

1. A drive coupling comprising a rotatable drive input member having blades and adapted to be connected to a dirve input shaft, and a drive output member having blades and adapted to be connected to a drive output shaft, the assembly being capable of functioning in the manner of a fluid coupling at rates of rotation above a predetermined rate, and a reactor member have blades and positioned in the flow path of fluid moving between said input and output members, the reactor member being mounted so as to be non - rotatable in the non - drive direction.

the non - drive direction.

6. A drive coupling according to any one of the preceding claims wherein said reactor member is mounted on a sleeve member adapted to be connected to the housing of a gear train and the drive output member is adapted to be connected to a drive output shaft extending through said sleeve.

7. A drive coupling substantially as described herein with reference to the accompanying drawings.

8. A drive transmission comprising a drive coupling according to any one of the preceding claims in combination with a constant mesh change speed gear train.

9. A vehicle comprising a turbocharged internal combustion engine in combination with a drive transmission according to claim 8.