GB2221272A

GB2221272A - Mechanically engaged four-wheel-drive vehicle using recirculating ball screw and nut actuation

Info

Publication number: GB2221272A
Application number: GB8908444A
Authority: GB
Inventors: Enzo Brusasco
Original assignee: RGB SpA
Current assignee: RGB SpA
Priority date: 1988-04-15
Filing date: 1989-04-14
Publication date: 1990-01-31
Also published as: ES1011251Y; GB8908444D0; FR2630055A1; IT214274Z2; ES1011251U; IT8853063V0; DE3912172A1

Abstract

A vehicle comprises two drive wheels (4) and two normally-driven wheels (6) mounted in an idling manner on the ends of axle shafts (9) which are connected to a differential assembly (8). The latter is connected to an engine-transmission assembly (3) via a propeller shaft (10) and a first disengageable coupling (11). A second disengageable coupling (12) is located between each driven wheel (6) and its associated axle shaft (9). Each disengageable coupling (11, 12) is operated between engaged and disengaged positions by means of a control device featuring an electromechanical linear actuator with a recirculating ball screw-nut screw coupling. …<??>The actuator may comprises an electric motor driving the nut of the coupling via reduction gearing, which in turn drives a rod linearly to engage or disengage the drive coupling (11) via a rocker arm. A microswitch may be provided adjacent the rocker arm to detect the engaged/disengaged positions. …<IMAGE>…

Description

k MECHANICALLY ENGAGED FOUR-WHEEL-DRIVE VEHICLE The present invention

relates to a mechanically engaged four-wheel-drive vehicle.

On vehicles, particularly motor vehicles, featuring an engageable four-wheel drive, the power plant usually comprises an engine-transmission assembly; two drive wheels fitted on to the ends of two axle shafts of a first. shaf t connected substantially directly to said exigitie-f-rittisrilissioti assembly; two normally-driven wheels; and a drive connecting said driven wheels to said engine-transmission assembly.

Said drive usually comprises shaf t, connected in wheels and assembly; a said dif f erentia 1 assembly; two axle shafts of a second normally idle mariner to said driven to respective outputs of a differential propeller shaft connected to an input of arid three (1 i s e riga gea b 1 e coup 1 i ngs, a f irst of which is designed to connect the propeller shaft to the engine- transmission assembly, arid the other two to connect the driven wheels integral with the respective axle shafts.

2 Oil known vehicles of the aforementioned type, cacti said coupling usually presents a pneumatic control device, usually comprising a vacuum tank designed, by means of solenoid valves, to enable axial distortion ofa diaphragm controlling engagement and disengagement of the coupling, arid having electronic control circuits for determining the coupling position arid operating sequence.

In addition to the relatively high-cost structure of the aforementioned pneumatic control device, diaphragm response also varies according to external pressure and temperature, with. the result that, when four-wheel drive performance is most needed (at high attitude, with a low external temperature), engagement is invari- ably impaired by the rigidity of the diaphragms (which) arid the increases alongside it fa 1 1 in temperature minimal difference between external pressure and that inside the vacuum tank.

The aim of the present invention is to provide a vehicle featuring an engageable four-wheeL drive, designed to overcome. the aforementioned drawbacks.

With this aim ill view, according to the present invention, there is provided a vehicle featuring air engageable four-wheel drive and comprising an engine-t ransmi ss ion 25 assemb Ly; two normal ly-driven wheels; arid a drive connecting said driven wheels to said enginetransmiss ion assembly; said drive comprising a differential assembly; two axle shafts connected in normally idle manner to sir id driven wheels arid to respective outputs of said differential assembly; it propeller shaft connected - 3 to all input of said differential assembly; three disengageable couplings, of which a first is located between said b ly, respective said art engaged arid the f act that e lectromechanica activating an lating ball between said A lion- 1 imiting propeller shaft arid said engine-trarismission assemarid the other two between said driven wheels and axle shafts; arid a control device for each coup 1 ing, designed to operate disengaged position; each said the same between characterised by control device comprises an 1 linear actuator having means for axially-mobile output member; a recircu screw-riut screw coupling being provided actuating means and said output member.

embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which Fig.1 Shows a ill accordance tion; Fi-. 2 shows a in Fig.1; it larger-scale side view of a second detail plan view of the power plant on a vehicle with the teachings of the present inven- Larger-scale plan view of a first detail Fig. 3 shows in Fig. 1; Fig. 4 shows 3; Fig.5 shows a section along line V-V ill Fig.4.

Number 1 ill Fig. 1 indicates a motor vehicle having a power plant 2 comprising an engine-transmission assembly 3; two drive wheels 4 fitted oil to the ends of respective to an output of engine-transtwo normally-driven wheels it front view of axle shafts 5 connected mission asserlib ty 3; and a detail in Fig.s 2 and 6 connectable to the output of engine-transmission assembly 3 via a drive indicated as a whole by 7.

Drive 7 comprises a differential assembly 8 having two outputs connected to two axle shafts 9, and an input connected to a propeller shaft 10. Drive 7 also comprises a first known type of disengageabLe coupling 11, usually a face gear coupling, located between one end of propeller shaft 10 and the output of enginetransmission assembly 3, and a further two known dis- engageable couplings 12, also usually face gear couplings, each located between a respective axle shaft 9 and respective wheel 6, which is supported on respective axle shaft 9 in such a manner as to normally turn idly in relation to the same.

As shown in Fig.2, coupling 11 comprises an outer casing 13 with two substantially coaxial outer flanges 14 and 15, 13 and that facing fLange 14.

the other (anticlockwise and a transverse pin 16 extending through casing located on the opposite side of flange 15 to Rotation of pin 16 one way or in Fig.2) about its own axis and in relation to casing 13, provides in known manner for respectively engaging or disengaging coupling 11. The outer end of pin 16 is fitted to the center portion of a rocker an end plate a microswitch to flange 14 arm 17 cooperates with surface 26 of flange 15 there is also connected 1 arm 17, a first arm 18 of which presents 19 cooperating with a push- button 20 of 21 supported on a bracket 22 connected via screw 23. A second arm 24 of Tocker a limit stop 25 connected to facing pin 16. To surface 26 a first arm of a substantially casing 13, supports 28a connected to via pin 29, and L-shaped bracket 27, the second arm of which. located outside arid substantially parallel with the axis of a control device or linear actuator arm 18 in the vicinity of plate 19 designed to turn arm 17 and pin 16 between an engaged position arid a disengaged position, contacting limit stop 25y as shown respectively by the continuous arid dotted lines in Fig.2. As shown in Fig-3, eacii coupling 12 is housed inside a casing 30 located inside respective wheel 6 and having a transverse pin 31 extending through casing 30 and designed, when turned one way or the other (clockwise in Fig.3) in relat-ion to casing 30, to respectively engage or disengage coupling 12 in known manner.

Th e outer end of pin 31 is f itt ed on to one end of a lever 32, tlic other end of which is connected via transverse i)ill 33 to a control device or linear actuator 281) designed to turn lever 32 and pill 31 between an engaged and disengaged position as shown respectively by the continuous and dotted lines in Fig.3.

Actuator 28b is supported in fixed manner on a bracket 34 integral with a tube shaft 9 and forming vehicle 1.

As shown in Fig.s 4 and 5, each of actuators 28a and 28b, indicated generically by 28, comprises a substantially cup-shaped outer casing 36 closed at one end by cover 37 and having a lateral wall defined by a projecting j)Iate 38 with studs 39 for securing actuator 28 to a support.

protecting respective axle part of the rear shaft of motor 6 - An inner wall 40 divides easing 36 into two axial- chambers, a first of which houses a reversible electric motor 41 having an output shaft 42 connected to the input of a reduction unit indicated as a whole by 43.

The second chamber of easing 36 houses a cylindrical recirculating ball nut screw 44 having external teeth 45 constituting the output gear of reduction unit 43. As shown in Fig.S, the opposite ends of nut screw 44 present two annular grooves 46 constituting the tracks of balls 47 of respective axial thrust bearings 48 connecting nut screw 44 in surface of easing 36 and cover 37. A screw SO is mounted for rotation,' via the interposition of balls 49, through nut screw 44, one end of which screw SO extends through 1S a hole SI in cover 37 and is fitted with a rod 52 constituting the output member of actuator 28.

Rod 52 is connected to rocker arm 17 or lever 32 via the interposition of a damping element, for which pLirpose., the free end of rod S2 is fitted in sliding manner, by means of a helical spring S3 coaxial with rod S2, with a cou p 1 in., 54, the stroke of which, in relation to rod S2, is determined by a pin 55, the intermediate portion of which engages a diametrical through hole 56 formed through rod S2, and the end portions of which 2S engage, in sliding manner, respective axial slots S7 formed through coupling S4. Coupling S4 is fitted to one end of bellows 58 having its other end connected to cover 37, and is closed at its free end by a cap Sq.fitted with a ring 60 engaged by pin 29 or 33.

In actual use, when the four-wheel drive is disengaged, rotary manner to the inner - 7 with rocker arm 17 and levers 32 positioned as shown by the dotted lines in Fig.s 2 arid 3, operation by the user of a connecting device (not shown) first provides for activating motor 41 of actuator 28a. blotor 41 turns nut screw 44 so its to axially shift rod 52 from the withdrawn (disengaged) position to the extracted (engaged) position, and so shift rocker arm 17 into the engaged position shown by the continuous line in Fig.2. In this position, plate 19 of rocker arm 17 presses button 20 of microswitch 21, which supplies a known control circuit (riot shown) with a signal indicating engagement of coupling 11. Said signal acts as an enabling signal for sequentially operating actuators 28b, which provide for engaging respective couplings 12, and so also driving wheels 6.

The above procedtire is performed in reverse for disengagenient.

Elect- romechanica 1 actuators 28 clearly substantially eliminating being impaired by, f ore, for of engagement temperature. Moreover, by virtue of reduction unit 43 it 11 (1 screw-out screw coupling 44-50, which in itself provides for a high reduction ratio, actuators 28 provide for high-power performance while at the same time employ- in., a relatively high-speed, low-cost motor 41.

provide, therearty possibility external nressure and 1

Claims

1) - A vehicle featuring an engageable four-wheel- dril,e, and c.imprising an engine-transmisson assembly two normally-driven wheels; and a drive connect ing said driven wheels to said engine-transmission assembly said drive assembly idle manner 10 outputs of shaf t assembly of which a shaf t and the other two and respective axle comprising a d 'f'erential two axle shafts connected in normally to said driven wheels and to respective said differential assembly; a propeller connected to an input of said differential three disengageable couplings first is located between said propeller and said engine-transmission assembly between said driven wheels shafts and a control device for each sa i d coupling designed to operate the s a m e between an engaged and disengaged position; characterised by the fact that each said control device comprises an electromechanical linear actuator having means for activating an axially-mobile output member a recirculating ball screw-nut screw coupling being provided between said actuating means and said output member 2) - A vehicle as claimed in Claim 1, characterised by the fact that each said control device also comprises il lever element hinged to said output member and fitted to a pin. designed, when turned between two distinct angular positions about its own axis, to engage or disengage the respective said coupling Y i A vehicle as claimed by the fact that said to the respective said interposition of damping means 4) - A vehicle as claimed in any one of the foregoing Claims, characterised by the fact that the device con trolling said first coupling comprises a device for determining said engaged and disengaged positions.

5) - A mechanically engaged four-wheel-drive vehicle, substantially as described and illustrated herein with reference to the accompanying drawings.

in Claim 2, characterised output member is connected lever element via the Published 1990a The Patent Office. State House. 66 71 High Holborn. London WC1R4TP Further copies maybe obtalnedfrom The Patent Office. Sales Branch. St Ma-y Cray. Orpington. Kent BR5 3RD Printed by Multiplex techniques ltd. St Mary Cray, Kent, Con. 1,87