GB1603633A

GB1603633A - Continuously variable transmissions

Info

Publication number: GB1603633A
Application number: GB1862877A
Authority: GB
Original assignee: REIMERS PIV ANTRIEB KG W
Current assignee: REIMERS PIV ANTRIEB KG W
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-11-25

Description

(54) CONTINUOUSLY VARIABLE TRANSMISSIONS (71) We, PIV ANTRIEB WERNER REIMERS KOMMANDITGESELL SCHAFT a German Company of Postfach 1960, D-6380 Bad Homburg, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to transmission assemblies, particularly for motor vehicles, having an input and an output and being of the kind, hereinafter referred to as being the kind specified, comprising in combination (1) a continuously variable transmission (c.v.t.) of the belt or chain type in which a belt or chain is entrained around first and second pulleys whose effective diameters can vary to change the ratio of the transmission, the first pulley being driven from said input, and (2) a three-element. spur-gear epicyclic gearing of which the planet carrier is drivable from the input, the sun gear is driven from the second pulley of the c.v.t. and the annulus drives said output.

The object of the present invention is to provide an improved transmission assembly of the kind specified.

According to the present invention a transmission assembly of the kind which has an input and an output and which comprises in combination (i) a continuously variable transmission (c.v.t.) of the belt or chain type, in which the belt or chain is entrained around a first and a second pulley set. the effective diameters of which can vary to change the transmission ratio. the first pulley set being driven by the input. and (ii) a three element spur-gear epicyclic gearing. the planet carrier of which is drivable from the input, the sun gear of which is driven by the second pulley set of the c.v.t. and the annulus of which drives the output. the transmission ratio setting of the c.v.t. being controllable from a reduction ratio (low) to an overdrive ratio (high), a reduction drive being arranged between the input and the planet carrier, a first clutch being associated with the reduction drive by which this reduction drive is couplable with and uncouplable from the input and a second clutch is arranged between the sun gear and the planet carrier of the epicyclic gearing, by which the epicyclic gearing can be locked up, the two clutches being controllable in such a way that both are disengaged, or so that when the one clutch is engaged the other is disengaged and vice versa whereby the direction of rotation and speed of rotation of the output are determined solely by controlling of the transmission ratio setting of the c.v.t. and of the two clutches is characterised in that; a) the first clutch is coaxial with the first pulley set and is physically located between the said input and the input of the reduction drive; b) the reduction ratio of the reduction drive corresponds to the said low ratio setting of the c.v.t. and; c) Rvlow + 0.2 R ' RVhigh (1-R) where RVIOW is the said low or reduction setting of the c.v.t. Rvhigh iS the said high overdrive setting of the c.v.t. and R A/A + S where A is the number of teeth of the annulus and S is the number of teeth of the sun gear of the epicyclic gearing.

The advantage of relating the c.v.t. and epicyclic ratios as set out above is that we obtain a sufficiently wide transmission ratio spread from reverse to the highest forward ratio, to operate the prime mover driving the assembly on an efficiency schedule which gives low fuel consumption.

In use, to obtain reverse, the first clutch is engaged and the c.v.t. put in its high ratio.

The sun gear is now rotating faster than the planet carrier so that the output will rotate in the reverse direction to the input. We have found that by choosing the ratio of the reduction drive to be equal to RVIOW and by the relationship between the c.v.t. ratios and the epicyclic ratios, we can obtain a useful reverse ratio.

With the first clutch engaged, at the ratio of the c.v.t. is reduced, the speed of the output in reverse will reduce until a stage will be reached when the annulus will be stalled and this will be the geared neutral position.

Further reduction in the ratio of the c.v.t.

until it reaches Rvl,, will provide a first regime in forward drive in which the output is rotating in the same direction as the input.

When the ratio of the c.v.t. is at RVIOWT the planet carrier and the sun gear are rotating at the same speed since the reduction ratio of the reduction drive for the planet carrier Rv10. The output will thus be rotating at the same speed as the input since if two members of the epicyclic gearing are rotating at the same speed the third member will also rotate at that speed.

With all the elements of the epicyclic gearing rotating at the same speed, the first clutch is disengaged and the second clutch is engaged. The engagement of the second clutch locks up the epicyclic gearing so that it rotates as a unit and the disengagement of the first clutch disengages the drive between the planet carrier and the input. The ratio of the c.v.t. can now be increased to RVhigh to obtain a high forward regime and the ratio of the assembly will be the ratio of the c.v.t.

alone.

It is envisaged that Rvlow and RVhjFh Will be the minimum and maximum ratios obtain able from the c.v.t. but it may be desired, for some reason, not to use the whole ratio spread of the c.v.t. in which case RVIOW and Rvhjgh would be the minimum and maximum ratios of the c.v.t. which were used and would depend on the control for the c.v.t.

Preferably the second clutch is physically located between the second pulley set of the c.v.t. and the planet carrier the planet carrier and the second clutch being coaxial with one another.

Preferably the second clutch is formed by the free end of the planet carrier, the pulley side adjacent thereto of the second pulley set and a clutch operating piston arranged between these.

The above preferable features enable a small clutch to be used because the clutch is disposed in a position where only a low torque has to be transmitted, further facilitating a compact over-all design of transmission assembly.

The invention will now be described in detail by way of example with reference to the accompanying drawings in which: FIGURE 1 is a diagram of an assembly embodying the invention; FIGURE 2 is a part longitudinal section through a practical embodiment of the assembly; FIGURE 3 is a diagram showing the over-all ratio of the transmission assembly plotted against the output speed of the c.v.t.

per 1000 rpm input; and FIGURE 4 is a section corresponding to part of Figure 2 but showing a modified design of second clutch.

Referring first to Figure 1, the assembly there shown in diagrammatic form has an input shaft 1 and an output shaft 2. The input shaft 1 is fixedly connected to a first pulley 3 of a c.v.t. of the belt or chain type. Fixed to the input shaft is one part of a clutch 4, the other part of which is carried by a gear 5 which is freely rotatably mounted on the input shaft 1.

The second and driven pulley of the c.v.t.

is indicated at 6 and is fixedly connected to a shaft 7 to which is connected the sun gear 8 of epicyclic gearing of the spur gear type.

The sun gear 8 meshes with a number of planet gears 9 which are carried by a planet carrier 10. The annulus gear of the gearing is indicated at 11 and is connected to the output shaft 2.

The planet carrier 10 is driven through a gear 13 which meshes with an idler gear 14, which in turn meshes with the gear 5. A clutch 12 is provided between the planet carrier and the driven c.v.t. pulley 6.

In a first regime, the clutch 4 is engaged and the clutch 12 is disengaged. The planet carrier 10 is driven at a low ratio relative to the input shaft 1 and this ratio is equal to RVIOW as described above.

When the c.v.t. is in its high ratio at Rvhjgh, the sun gear will be driven faster than the planet carrier so that the annulus will rotate in the reverse direction. The relation set out above with regard to RVI,,, Rvhjgh and R ensures that the speed of rotation of the output shaft 2 in reverse is usable speed and the output shaft 2 may, for example, rotate at between 300 and 400 r.p.m. per 1,000 r.p.m. of the input shaft 1. This 300 to 400 r.p.m. of the output shaft will be when the c.v.t. is at its high ratio, Rvhjgh. Figure 3 shows that the over-all ratio of the transmission assembly is 3.3 when operating in reverse at Rvhjgh.

As the ratio of the c.v.t. is reduced, the speed of the output shaft 2 in reverse will decrease until the annulus 11 will be stalled when the assembly will have a geared neutral position. This is shown by the vertical dash line '0' in Figure 3. Further reduction in the ratio of the c.v.t. down to RVIOW will cause the output shaft 2 to rotate in the forward direction and since the ratio of the reduction drive 5, 14, 13 is the same as RVIOW when the ratio of the c.v.t. is Rv10, the planet carrier 10 and the sun gear 8 are rotating at the same speeds. As a result, the annulus 11 must be rotating at the same speed and therefore the planet carrier and annulus are rotating at the same speed this occurs at an over-all ratio of 2 in Figure 3. At this point, the clutch 12 is engaged and the clutch 4 disengaged. Engagement of the clutch 12 locks up the epicyclic gearing and disengagement of the clutch 4 disconnects the planet carrier from the input shaft 1. The over-all ratio of the assembly is now the ratio of the c.v.t. and the ratio of the latter can be increased to Rvhjgh to give, for example, 2,000 r.p.m. of the output shaft 2 for 1,000 r.p.m. of the input shaft 1.

It will be seen that the speed and direction of rotation of the output shaft 2 are controlled solely via the clutches 4 and 12 and control of the ratio of the c.v.t.

Referring now to Figure 2, the assembly there shown is mounted in a housing 20 and includes an input shaft 21 which is received in forward and rear bearings 22 and 23 in the housing. At its forward end, the input shaft 21 has a spring and friction torsional damper 24 through which it is driven from a vehicle engine.

Mounted at the righthand end of the input shaft 21 is a first pulley 25 of a belt or chain type c.v.t. One side 26 of the pulley is fixed, the other side, 27, of the pulley is movable between the full and dotted line positions by means of hydraulic fluid introduced into a chamber 28 acting on a piston 29 which is connected to a sleeve 30 integral with a side 27. A pair of belville springs 31 urges the side 27 towards side 26. The pulley 25 is keyed to rotate with the shaft 21.

Adjacent to the pulley 25 a chain wheel 81 is rotatably mounted on the shaft 21 via a bearing 32. Secured to the chain wheel 81 is an annular member 33 of L-section one limb 34 of which provides a conical clutch surface 35 for a first clutch 82. A housing 36 is splined at 37 to the shaft 21 and is formed with an annular cylinder 38 in which is slidable an annular piston 39 carrying sealing rings 40 to seal with the walls of the cylinder.

The piston 39 carries a conical friction surface 41 which is arranged to co-operate with the clutch surface 35. Hydraulic fluid can be introduced into the cylinder 38 through a passage 38a from a pump 42 described in more detail below.

The driven pulley of the c.v.t. is shown at 43 and comprises a fixed side 44 and a movable side 45, the latter being movable by means of hydraulic fluid introduced into a chamber 46 and acting between the side 45 and a fixed piston 47. Belville springs 48 urge the side 45 to its lefthand position. A chain or belt (not shown) extends between the pulleys 25 and 43 and in a well known manner, the sizes of the pulleys can be varied to vary the ratio of the c.v.t. constituted by the two pulleys.

Formed in the lefthand face of the side 44 is an annular cylinder 50 in which is slidable a piston 51 carrying a conical friction surface 52 of a second clutch 83. Relative rotation between the side 44 and the piston 51 is prevented by dowels 53. Hydraulic fluid can be introduced into the cylinder 50 behind the piston 51 through passages 54 in the side 44 and 54a in an intermediate shaft 55 on which the pulley 43 is mounted. The shaft 55 is supported in a forward bearing 56 and a rear bearing 57.

To the left of the piston 51 there is mounted on the shaft 55 the sun gear 59 of epicyclic gearing indicated generally at 60.

The gearing includes a planet carrier 61 which is rotatably mounted on the intermediate shaft 55 by means of a bearing 62. The planet carrier is provided at its outer periphery with a conical surface 63 to engage with the friction surface 52. The planet carrier carries a number of planet gears, one of which is shown at 64 mounted on pins 65 by needle roller bearings 66. The planet gears mesh with an annulus gear 67 which is carried on a shaft 68 supported by bearings 58 and 58a in the housing. The shaft 68 has a counterbore 69 in which one end of the shaft 55 is supported by the bearing 56. The shaft 68 carries an output gear 71 and constitutes the output shaft of the assembly.

Reverting now to the gear pump 42, this comprises an outer toothed member 72 arranged eccentrically with respect to the axis of the input shaft 21 and an inner toothed member 73 which is rotatable from the input shaft 71 by means of a key or ball drive 74.

As the shaft 21 rotates, the gear 73 is rotated thus pumping oil between the teeth on the gears 72 and 73 to provide a source of pressure to operate the clutches 82 and 83 and the pulleys of the c.v.t.

The planet carrier 61 is provided on its outer periphery with sprocket teeth 77 and these engage a chain 78 which is engaged around the chain wheel 81. The sizes of the chain wheel 81 and the planet carrier are such as to provide a reduction drive so that the planet carrier is driven, relative to the input shaft 21, when the clutch 33, 39 is engaged, at a ratio which corresponds to Rq,,.

The operation of the assembly shown in Figure 2 is exactly as described in Figure 1, the clutch 4 of Figure 1 is replaced by the clutch 82 and the clutch 12 of Figure 1 is replaced by the clutch 83 of Figure 2. The gear drive 5, 13, 14 of Figure 1 is replaced by the chain drive 81, 77 and 78 of Figure 2.

In the practical embodiment shown in Figure 2, the clutch 83, which is in effect interposed between the carrier 61 and the sun gear 59 is physically disposed between the pulley 43 and the epicyclic gearing 60.

Part of this clutch namely the cylinder 50 and piston 51, is disposed physically within the pulley 43. Also part of the clutch, namely the conical surface 63 and the friction surface 52, is disposed within the toothed member carrying sprocket teeth 77 which forms a part of the reduction drive. This part of the reduction drive is fixed to and in effect forms part of the planet carrier 61. This arrangement of parts is particularly effective in its use of space so that the transmission as a whole and particularly that part of the transmission along the axis of shaft 55 can be kept short.

The invention is concerned solely with the structure and configuration of the transmission assembly and for that reason a control system for the transmission is not described in detail. However in practice a control system should be provided. The control system receives hydraulic pressure from the pump 42 and distributes this pressure selectively in accordance with operating conditions of the transmission to the hydraulic cylinders which operate the two clutches 82 and 83 and the pulleys 25 and 43. The control system thus causes the ratio of the c.v.t. and the selective engagement of the clutches 82 and 83 to be adjusted in accordance with transmission requirements.

In place of the cone clutches 82 and 83 there may be substituted plate clutches and a plate clutch for use as a replacement to clutch 83 is shown in Figure 4. To facilitate a comparison between Figure 2 and Figure 4 those parts of Figure 4 which are similar to corresponding parts in Figure 2 are identified by corresponding reference numerals but with the addition of 100. In Figure 4 a shaft 155 carries the fixed side 144 of the driven pulley 143 to a c.v.t. An annular cylinder 150 is provided in the pulley side 144 and a piston 151 is slidable in and sealed with respect to the cylinder 150. Rotation of piston 151 with respect to the side 144 is prevented by means of a splined sleeve 153 carried by the side 144 and drive lugs 91 on the outer periphery of the piston 151 and in engagement with the sleeve 153. Hydraulic fluid can be introduced into the cylinder 150 behind the piston 151 through passages 154 in the side 144 and 154a in the shaft 155.

The splined sleeve 153 also carries to the left of the piston 151 a clutch pressure plate 92 which is splined to the sleeve 153 and is held against axial movement awav from the piston 151 by a circlip 93. The piston 151 and pressure plate 92 have co-operating friction faces 152 between which lies an annular clutch driven plate 163.

The planet carrier 161 has an inner annular extension 94 to which the inner periphery of the driven plate 163 is splined. The planet carrier 161 is also provided around its outer periphery with sprocket teeth 177 and these engage a chain 178.

In operation of the clutch shown in Figure 4 the cylinder 150 is pressurised to force the piston 151 towards pressure plate 92 and thereby frictionally grip the driven plate 163 between the friction surfaces 152.

It will be seen that the clutch shown in Figure 4 could be substituted for the clutch 83 of Figure 2 without any substantial alterations to the lay-out of the transmission assembly. In a similar way a plate clutch corresponding to that shown in Figure 4 could be substituted for the clutch 82 of Figure 2. With the arrangement of Figure 4, the clutch shown in the drawing is disposed in a similar position to the clutch 83 of Figure 2 so that the same advantages of compactness are achieved.

WHAT WE CLAIM IS: 1. A transmission assembly of the kind which has an input and an output and which comprises in combination (i) a continuously variable transmission (c.v.t) of the belt or chain type, in which the belt or chain is entrained around a first and a second pulley set, the effective diameters of which can vary to change the transmission ratio, the first pulley set being driven by the input, and (ii) a three element spur-gear epicyclic gearing, the planet carrier of which is drivable from the input, the sun gear of which is driven by the second pulley set of the c.v.t. and the annulus of which drives the output, the transmission ratio setting of the c.v.t. being controllable from a reduction ratio (low) to an overdrive ratio (high), a reduction drive being arranged between the input and the planet carrier, a first clutch being associated with the reduction drive by which this reduction drive is couplable with and uncouplable from the input, and a second clutch is arranged between the sun gear and the planet carrier of the epicyclic gearing, by which the epicyclic gearing can be locked up, the two clutches being controllable in such a way that both are disengaged, or so that when the one clutch is engaged the other is disengaged and vice versa whereby the direction of rotation and speed of rotation of the output are determined solely by controlling of the transmission ratio setting of the c.v.t.

and of the two clutches, characterised in that: a) the first clutch is coaxial with the first pulley set and is physically located between the said input and the input of the reduction drive; b) the reduction ratio of the reduction drive corresponds to the said low ratio setting of the c.v.t. and: c) Rvl,, + 0.2 R c Rvhjgh (l - R) where RVlow is the said low or reduction setting of the c.v.t. Rvhjgh is the said high overdrive setting of the c.v.t. and R=A/A + S where A is the number of teeth of the annulus and S is the number of teeth of the sun gear of the epicyclic gearing.

2. A transmission assembly as claimed in Claim 1, in which the second clutch is physically located between the second pulley set of the c.v.t. and the planet carrier the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. is disposed within the toothed member carrying sprocket teeth 77 which forms a part of the reduction drive. This part of the reduction drive is fixed to and in effect forms part of the planet carrier 61. This arrangement of parts is particularly effective in its use of space so that the transmission as a whole and particularly that part of the transmission along the axis of shaft 55 can be kept short. The invention is concerned solely with the structure and configuration of the transmission assembly and for that reason a control system for the transmission is not described in detail. However in practice a control system should be provided. The control system receives hydraulic pressure from the pump 42 and distributes this pressure selectively in accordance with operating conditions of the transmission to the hydraulic cylinders which operate the two clutches 82 and 83 and the pulleys 25 and 43. The control system thus causes the ratio of the c.v.t. and the selective engagement of the clutches 82 and 83 to be adjusted in accordance with transmission requirements. In place of the cone clutches 82 and 83 there may be substituted plate clutches and a plate clutch for use as a replacement to clutch 83 is shown in Figure 4. To facilitate a comparison between Figure 2 and Figure 4 those parts of Figure 4 which are similar to corresponding parts in Figure 2 are identified by corresponding reference numerals but with the addition of 100. In Figure 4 a shaft 155 carries the fixed side 144 of the driven pulley 143 to a c.v.t. An annular cylinder 150 is provided in the pulley side 144 and a piston 151 is slidable in and sealed with respect to the cylinder 150. Rotation of piston 151 with respect to the side 144 is prevented by means of a splined sleeve 153 carried by the side 144 and drive lugs 91 on the outer periphery of the piston 151 and in engagement with the sleeve 153. Hydraulic fluid can be introduced into the cylinder 150 behind the piston 151 through passages 154 in the side 144 and 154a in the shaft 155. The splined sleeve 153 also carries to the left of the piston 151 a clutch pressure plate 92 which is splined to the sleeve 153 and is held against axial movement awav from the piston 151 by a circlip 93. The piston 151 and pressure plate 92 have co-operating friction faces 152 between which lies an annular clutch driven plate 163. The planet carrier 161 has an inner annular extension 94 to which the inner periphery of the driven plate 163 is splined. The planet carrier 161 is also provided around its outer periphery with sprocket teeth 177 and these engage a chain 178. In operation of the clutch shown in Figure 4 the cylinder 150 is pressurised to force the piston 151 towards pressure plate 92 and thereby frictionally grip the driven plate 163 between the friction surfaces 152. It will be seen that the clutch shown in Figure 4 could be substituted for the clutch 83 of Figure 2 without any substantial alterations to the lay-out of the transmission assembly. In a similar way a plate clutch corresponding to that shown in Figure 4 could be substituted for the clutch 82 of Figure 2. With the arrangement of Figure 4, the clutch shown in the drawing is disposed in a similar position to the clutch 83 of Figure 2 so that the same advantages of compactness are achieved. WHAT WE CLAIM IS:

1. A transmission assembly of the kind which has an input and an output and which comprises in combination (i) a continuously variable transmission (c.v.t) of the belt or chain type, in which the belt or chain is entrained around a first and a second pulley set, the effective diameters of which can vary to change the transmission ratio, the first pulley set being driven by the input, and (ii) a three element spur-gear epicyclic gearing, the planet carrier of which is drivable from the input, the sun gear of which is driven by the second pulley set of the c.v.t. and the annulus of which drives the output, the transmission ratio setting of the c.v.t. being controllable from a reduction ratio (low) to an overdrive ratio (high), a reduction drive being arranged between the input and the planet carrier, a first clutch being associated with the reduction drive by which this reduction drive is couplable with and uncouplable from the input, and a second clutch is arranged between the sun gear and the planet carrier of the epicyclic gearing, by which the epicyclic gearing can be locked up, the two clutches being controllable in such a way that both are disengaged, or so that when the one clutch is engaged the other is disengaged and vice versa whereby the direction of rotation and speed of rotation of the output are determined solely by controlling of the transmission ratio setting of the c.v.t.

planet carrier and the second clutch being coaxial with one another.

3. A transmission arrangement as claimed in Claim 2 in which the second clutch is formed by the free end of the planet carrier, the pulley side adjacent thereto of the second pulley set and a clutch operating piston arranged between these.

4. A transmission assembly substantially as described with reference to and as illustrated by Figure 2 of the accompanying drawings.

5. A transmission assembly substantially as described with reference to and as illustrated by Figure 2 when modified as illustrated in Figure 4 of the accompanying drawings.