WO2009130553A1

WO2009130553A1 - Vehicle transmission arrangements

Info

Publication number: WO2009130553A1
Application number: PCT/IB2009/000580
Authority: WO
Inventors: Ville Viitasalo
Original assignee: Valtra Oy AB
Current assignee: Valtra Oy AB
Priority date: 2008-04-23
Filing date: 2009-03-24
Publication date: 2009-10-29
Anticipated expiration: 2010-10-23
Also published as: GB0807345D0

Abstract

A vehicle transmission arrangement comprising a multi-ratio gearbox (10) is provided. The gearbox drives one or more wheels of the vehicle from an associated engine (12) via a drive disconnection means. A control system (110) is arranged to ensure that, when the vehicle comes to rest (a) the drive disconnect means is set to a condition in which no power is transmitted from the engine to the gearbox, and (b) more than one gear ratio is engaged in the gearbox to lock up the gearbox and hence hold said one or more wheels against rotation thus holding the vehicle at rest.

Description

DESCRIPTION

VEHICLE TRANSMISSION ARRANGEMENTS

This invention relates to vehicle transmission arrangements and is concerned with the problem of preventing rolling of vehicles which come to rest or change their direction of travel whilst on an incline.

It is an object of the present invention to provide a vehicle transmission arrangement which at least mitigates the above rolling problem.

Thus according to the present invention there is provided a vehicle transmission arrangement including:-

a multi-ratio gearbox which drives one or more wheels of the vehicle from an associated engine via a drive disconnection means, and a control system arranged to ensure that, when the vehicle comes to rest, a) the drive disconnect means is set to a condition in which no power is transmitted from the engine to the gearbox, and b) more than one gear ratio is engaged in the gearbox to lock up the gearbox and hence hold said one or more wheels against rotation thus holding the vehicle at rest.

In such an arrangement the drive disconnection means may comprise a main drive clutch or an input gearbox section which includes one or more drive clutches or an input gearbox section which can be set to operate in a geared-neutral condition in which no power is transmitted through the input gearbox section.

The multi-ratio gearbox may comprise a shuttle section having forward and reverse drive clutches to drive the vehicle in a forward or reverse drive direction in series with a second gearbox section, the control system being arranged to ensure that, when the vehicle comes to rest,

a) the input gearbox section is set to a condition in which no power is transmitted through the input gearbox section to the shuttle section, b) both the forward and reverse clutches are engaged to lock-up the shuttle section, and c) a gear ratio is engaged in the second gearbox to ensure a drive connection between said one or more wheels of the vehicle and the shuttle section to lock the vehicle against movement.

The input gearbox section may be in the form of a multi-ratio powershift gearbox with one or more clutches which when disconnected disconnect drive through the input gearbox. An example of such an arrangement is shown in the Applicant's co-pending UK patent application no. GB0709636.5.

Alternatively the input gearbox section may be in the form of a CVT which can be set in a geared neutral condition in which no power is transmitted through the CVT. An example of such an arrangement is shown in the Applicant's co-pending UK patent application no. GB0709635.7.

The present invention also provides a vehicle transmission arrangement including:-

an input gearbox section, a shuttle section and a second gearbox section in series to drive one or more wheels of the vehicle, the shuttle section including forward and reverse drive clutches to drive the vehicle in a forward or reverse drive direction, and a control system arranged to ensure that, when the vehicle comes to rest,

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which :-

Figure 1 shows diagrammatically the layout of a CVT form of transmission arrangement in accordance with the present invention;

Figure 2 shows diagrammatically a five speed power shift transmission arrangement in accordance with the present invention;

Figure 3 shows a tabular summary of the engagement sequence of the clutches of the powershift unit of figure 2, and

Figure 4 shows diagrammatically the simplest form of transmission arrangement in accordance with the present invention;

Referring to the drawings, a tractor transmission arrangement in accordance with the present invention has an input transmission section in the form of CVT 10 with an input shaft 11 driven from an engine 12. The input shaft drives an epicyclic gear 13 , a forward/reverse shuttle stage 14 and an further selectively engageable gear train 15 all in series. Gear train 15 in turn drives the front and rear wheels 8 and 9 via differentials 8a and 9a respectively.

The epicyclic gear 13 has three compound planets gears 16, 17, and 18 which rotate in unison at all times and are supported from a common carrier 19. Planets 16 and 17 engage sun gears 20 and 21 respectively which can be coupled with input shaft 11 via hydraulically operated clutches C2 and Cl respectively which are provided with pressurised hydraulic fluid from a hydraulic control circuit indicated diagrammatically at 111 in Figure 1 via lines 112 and 113 respectively. Hydraulic control circuit 111 is in turn controlled by electronic control system 110 which receives signals from various functions of the associated tractor. The third planet gear 18 engages a sun gear 22 mounted on an output shaft 23 of the epicyclic gear which is connected with the shuttle stage 14.

A hydraulic pump/motor loop 24, which include a variable displacement pump 25 connected with a motor 26, drives the planet carrier 19 from the input shaft 11 via gears 27, 28, 29, 30, 31,

32.

The epicyclic gear is designed to provide a continuous variation of ratio from a geared neutral condition in which the output shaft 23 is not rotating up to a ratio of say 2.2 :1 or 2.6:1 as follows.

Initially clutch Cl is engaged which drives sun 21 from the input shaft 11 and the carrier is driven by the pump/motor loop 24 at speeds varying from the maximum negative speed of rotation of the carrier (i.e. with the carrier rotating at its maximum speed in the opposite direction to the direction of rotation of the engine), when the geared neutral condition exists, up to the maximum positive speed of the carrier (i.e. with the carrier rotating at its maximum speed in the same direction as the engine). This provides a ratio range of 0 to 1.

The clutch C2 is then engaged which drives sun 20 from the input shaft 11 and carrier 19 is driven by the pump/motor loop 24 from the maximum positive speed of rotation of the carrier to the maximum negative speed of rotation of the carrier. This provides the ration range of 1 to

2.2.

The operative ratio of CVT 10 can be controlled automatically (in any suitable known manner) by control system 110 dependent on a wide range of control parameters or controlled manually by a lever 114 which is connected with control system 110 and is moveable between a zero ratio position 114' (so-called geared neutral) and a position 114" which corresponds to is highest ratio of 2.2 or 2.6. The epicyclic forward/reverse shuttle 14 has a sun gear 33 on shaft 23 and a sun gear 37 on the output shaft 36. Planet gears 35 and 36 are mounted on a carrier 40 and a reverse idler 34 connects gears 33 and 35. Gears 36 and 27 also mesh without the use of an idler. Forward drive is engaged by engaging clutch 38 which locks the carrier 40 to the shaft 36. Reverse is engaged by engaging clutch 39 which locks the carrier 40 to the transmission housing.

Clutches 38 and 39 are again supplied with pressurised fluid from hydraulic control circuit 111 via lines 115 and 116 respectively under the control of a control lever 117 connected with control system 110 drive and moveable between forward, neutral and reverse drive selecting positions F,N & R respectively.

Shaft 36 drives the further gear train 15 which is configured to give the required overall ratio range of the tractor. Li the arrangement shown gears 41, 42, and 43 rotate with a shaft 49. Gear 41 meshes with gear 48 on shaft 36 to drive shaft 49 and gears 42 and 43 mesh with gears 44 and 45 and can be coupled to a differential pinion shaft 46 by a sliding coupler 47 (see arrow H) to provide a high gear ratio H to shaft 46 via gears 42 and 44, which is used principally for road work and a low gear ratio M (see arrow M) via gears 43 and 45 which provides maximum tractive force and is used principally for field work.

Gears 50 and 51 also surround shaft 46. Gear 51 can be coupled to shaft 46 (see arrow LL) using sliding coupler 53 to engage an even lower gear ratio LL via gears 43, 45, 54, 55, 56, and 51. If sliding coupler 57 is used to couple gear 50 to shaft 46 (see arrow G) the PTO shaft 58 is driven via gear train 50, 59, 60, 61 and 62 at a speed G proportional to the ground speed of the tractor.

These couplers 47, 53 and 57 are moved by fluid pressure operated rams (not shown) supplied via lines 118, 119 and 120 respectively (shown diagrammatically in Figure 2) from control circuit 111. The operation of couplers 47, 53 and 57 to provide ratios H,M and LL and also the PTO ground speed G is controlled by a lever 121 moveable between positions H, M, LL and G.

Gear 52 on shaft 46 drives the front wheel drive shaft 63 via gear 64 and front wheel drive clutch 65. PTO shaft 58 can be driven from the input shaft 11 via a hydraulic clutch 66 and either gear train 67, 68 or 69, 70 using sliding coupler 71. Gear train 67, 68 gives a PTO shaft speed of 1000 r.p.m. at a specified engine speed whereas gear train 69, 70 gives a PTO shaft speed of 540 r.p.m. at the specified speed.

In accordance with the presenting invention, when the tractor comes to rest the electronic control system 110 ensures that both clutches Cl and C2 are disengaged so that no power is transmitted through CVT 10, that both clutches 28 and 39 are engaged to lock-up the shuttle stage 14 and that either ratio H, M or LL is engaged in gear train 15. This ensures that there is a positive drive connection between the locked-up shuttle stage 14 and the wheels of the tractor. This ensures that the tractor cannot roll if the vehicle has come to a reset on an incline.

In order to set the tractor in motion again, the driver will then select in which direction he wishes to travel using shuttle lever 117 and the non-operative clutch 38 or 39 will then be disengaged to allow the tractor to move away from rest in the required direction and in an appropriate ratio for the load on the tractor under the control of system 110.

The present invention the CVT is also applicable to a multi-ratio powershift transmission of the form shown in Figure 2.

In the powershift transmission of Figure 2 hydraulic pump loop 24 of Figure 1 is replaced by a mechanical gear loop 80 which drives carrier 19 from input shaft 11 via gears 81, 82, 83, and 84 using clutch C3 and which holds carrier stationary using clutch C4. Figure 3 shows in tabular form the engagement sequence of the clutches Cl, C2, C3 and C4 which gives the five ratios of the powershift provided by the epicyclic 13 and gear loop 80. Thus to engage the first ratio clutches Cl and C4 are actuated and to engage the second ration clutches Cl and C3 are actuated. The third ratio is engaged by actuating clutches Cl and C2 and the fourth ratio is engaged by actuating clutches C2 and C3. The fifth ratio is engaged by actuating clutches C2 and C4. Also additional sliding coupler 90 is provided so that shaft 49 can be driven either via gears 91 and 41 or via gears 92 and 42 thus doubling the number of ratios which the further gear train 15 can provide.

The additional clutches C3 and C4 and the additional coupler 90 are again all hydraulically controlled from hydraulic circuit 111 via lines 122, 123 and 124 respectively. The operative ratio of the multi-ratio powershift transmission can again be controlled automatically by control system 110 or can be controlled manually using a lever 125 which is selectively moveable between five positions. The coupler 90 is controlled automatically or manually by a two position button or switch 126 which can select the two ratios provided coupler 90.

In accordance with the present invention, when the tractor comes to rest the electronic control system 110 ensures none of the clutches Cl to C4 is engaged so no power is transmitted through the powershift transmission, that both clutches 38 and 39 are engaged to lock up the shuttle stage 14, that coupler 90 is engaged , and that either ratio H, M or LL is engaged in gear train 15. This again ensures that the tractor cannot roll if it comes to rest on an incline. Again, when the tractor moves away from rest, the non-operative clutch 38 or 39 is disengaged so that he tractor can move away from rest in the required direction and in the appropriate ratio for the load on the tractor under the control of system 110.

In its simplest form, a vehicle transmission in accordance with the present invention is as shown in Figure 4. This shows an engine 200 which drives wheels 203 via a multi-ratio transmission 201 (which includes a forward/reverse function) and a drive disconnection means 202 (eg a drive clutch). The transmission 201 and drive disconnection means 202 are controlled by an electronic control system 204 and a hydraulic circuit 205. The operative ratio of transmission 201 may be automatically controlled or selected using a lever 206 and the direction of travel is selected by lever 207.

In this simple arrangement, when the vehicle comes to rest the control system 204 ensures that the disconnection means 202 is disengaged and more than one ratio is engaged in transmission 201 in order to lock up the transmission 201 and hence hold the vehicle against rolling. When the vehicle pulls away from rest the engagement of the disconnection means 202 and the disengagement of all but one of the ratios in the transmission 201 is co-ordinated by the control system 204 to avoid rolling of the vehicle.

Claims

1. A vehicle transmission arrangement including: -

2. A transmission arrangement according to claim 1 in which the drive disconnection comprises a main drive clutch or an input gearbox section which includes one or more drive clutches or an input gearbox section which can be set to operate in a geared-neutral condition in which no power is transmitted through the input gearbox section.

3. A transmission arrangement according to claim 1 or 2 in which the multi-ratio gearbox comprises a shuttle section having forward and reverse drive clutches to drive the vehicle in a forward or reverse drive direction in series with a second gearbox section, the control system being arranged to ensure that, when the vehicle comes to rest,

4. A transmission arrangement according to claim 2 or 3 having an input gearbox section in the form of a multi-ratio powershift gearbox with one or more clutches which when disconnected disconnect drive through the input gearbox.

5. A transmission arrangement according to claim 2 or 3 having an input gearbox section in the form of a CVT which can be set in a geared neutral condition in which no power is transmitted through the CVT.

6. A vehicle transmission arrangement including:-

a first gearbox section, a shuttle section and a second gearbox section in series to drive one or more wheels of the vehicle, the shuttle section including forward and reverse drive clutches to drive the vehicle in a forward or reverse drive direction, and a control system arranged to ensure that, when the vehicle comes to rest,

a) the first gearbox section is set to a condition in which no power is transmitted through the first gearbox section to the shuttle section, b) both the forward and reverse clutches are engaged to lock-up the shuttle section, and c) a gear ratio is engaged in the second gearbox to ensure a drive connection between said one or more wheels of the vehicle and the shuttle section to lock the vehicle against movement.

7. A vehicle transmission arrangement constructed and arranged substantially as hereinbefore described with reference to and as shown in Figures 1 or 2 and 3 or 4 of the accompanying drawings.