Patent GB-640673-A (GB)
Title: Improvements in vehicular power-transmission mechanism
IPC: F16H48/30
Filed: 1947-11-27
Abstract: 640,673. Change-speed gear. CLERK, R. C. Nov. 27, 1947, No. 31474. [Class 80(ii)] [Also in Group XXXI] In a motor vehicle having steerable wheels and two driving wheels drive distributing means are provided for enabling the driving wheels, which are driven by the same motor, to rotate at different speeds, the means including two controllable slipable clutch devices between the motor and the driving wheels, and control means are adapted to operate, in response to various appreciable displacement of the steering wheels, to cause the clutch devices for the inner driving wheel to have a torque-transmission capacity which is lower than that of the other clutch device but which has a substantial value. Means may be provided which are operable for changing, or responsive to change in, the torque developed by the motor and arranged to increase the torque-transmission capacity of the clutch devices as the motor torque increases. Change-speed transmission gearing may be provided between the motor and the drive distributing means and control means operable for changing, or responsive to change in, the ratio of the gearing may be arranged to increase the - torque-transmission capacity of the clutch devices when the gearing is changed to a lower-speed ratio. As shown in Fig: 1 the wheels 17-0, 17-N are driven from all internal combustion engine 14 through a gear-box-15 a bevel pinion 13 meshing with a crown wheel 12. The crown wheel 12 carries a cage 11 journalled in a gear casing 10 and .having two driving elements 19-O, 19-N of electromagnetic clutches adapted to operate driven elements 18-O, 18-N connected by shafts 16-O, 16-N to the driven wheels. The electromagnetic clutches may be of the torque assisted type described in Specification 625,277 or of the type described in Specification 599,540. One end of each exciting element of the clutch is earthed and the other ends are connected to a source of supply 31 through brushes 21-0, 21-N engaging slip rings 20-O, 20-N. The source of supply 31 is earthed at one side and connected at the other side through a tapped resistor 37, a conductor 30 to two contacts 29-O ,29-N on a slider 23 engaging rheostats 22-0, 22-N and to fixed contact 36. The contact 36 is engaged by movable contacts 32-O, 32-N connected, respectively, to contacts 28-O, 28-N on the slider 23 engaging the rheostats 22-O, 22-N. The contacts 32-O; 32-N are moved in and out of engagement with the contact 36 by members 33, 34 actuated by the drag link 35 of the vehicle steering mechanism. The arrangement is such that on steering the vehicle to one side, the clutch on that side receives reduced current which reduces the torque transmission capacity of that clutch. The slider 23 is coupled by a rod 24 to a spring-loaded bellows 25 communicating with the engine induction manifold 27, the arrangement being such tha ' t ' .a reduction in induction vacuum, corresponding to an increase in engine torque, reduces the resistance in the current supplied to each clutch, thus producing reduced torque transmission capacity of the clutches. When the motor is not throttle controlled, the slider may be coupled to the accelerator or equivalent motor control-..The drive distributing gearing, Fig. 2, has two speeds. A pinion 40 meshes with. a crown wheel 41 having a cage having two annular gear rings 44-O, 42-N., These gear rings respectively engage planet gears 50-O, 50-N on carriers e 49-O, 49-N on half, shafts 45-O, 45-N, the planet gear also engaging sun whee1s 51-O, 51-N on sleeves 52-O, 52-N carrying armature discs 53-O, 53-N each disc having two exciting coils, one of which operates as a clutch and the other as a brake, as described in Specification 599,540. In operation by excitation of a winding: H.O.S., for example, the gearing becomes locked and the drive from the crown wheel 41 to the half shaft 45-O is direct.. If, however, a winding L.N.S. is excited the sleeve 52-N is held from rotation and the epicyclic gearing operates as reduction gearing the rotation of the half shaft 45-N being slower than that of the crown wheel. Thus by exciting the windings L.O.S., L.N.S., instead of H.O.S. H.N.S., the torque transmitting capaciting of the drivedistributing gearing is reduced. The circuit shown in Fig. 3 is for controlling the drive dstributing gearing, Fig. 2, for effecting gear change, varying the torque transmission capacity of the gearing with variation in torque and emergency braking of the driving wheels. The output of a generator 85 driven by the -vehicle engine is earthed at one side and at the other side is connected through a switch 88, rheostats 89, 90 to fixed contacts 91, 92. The rheostats 89 is initially adjusted and the rheostat 90 is variable under the control of bellows 93 to vary the resistance upon variation of torque. The windings L.N.S., L.O.S., H.N.S., H.O.S. are coupled in series with resistors in parallel with switches 83-N, 83-0, 84-N, 84-0 which are biassed to a closed position and to a fixed contact. A control member 70 is adapted to slide switch members 71, 72 in direction L from the neutral position shown to excite the windings L.O.S., L.N.S. from the generator and thus to engage the drive distributing gearing in low gear to each half shaft. De-magnetizing pulses for the exciting windings are effected through fixed contacts on return movement of the control member 70. Movement of the member 70 in the direction H effects a high gear drive for each half shaft by excitation of the windings H.O.S., H.N.S. with de-magnetizing pulses on return movement. Opening of any of the switches 83-N. 83-0; 84-N, 84-0 will place in circuit the respective resistor and this will effect a reduced excitation for the appropriate winding. The switches are operated by rotation of the steering column 94, Fig. 5. the column having a longitudinal groove 95 which is engaged by one arm of each four bell-crank levers pivoted on a pin 100, the other arm of each bell-crank operates the respective switch shown as 83-N. A return spring is fitted on the pin 100 such that in straight steering the bell-cranks do not impede the switches. To effect emergency braking all the windings are excited together from a battery 107, Fig. 2, through sliding members 108, 110 operated by a member 109 when the drive gearing is in either high or low speed. As shown in Fig. 7 all four wheels, the wheels 112-O; 112-N being steerable, are driven from an engine 115 through gearing 116, 117, a shaft 118, reduction gearing 120 and a main change speed gear box 119 to drive distributing gears 113, 114, which are each of the form shown in Fig. 2, on the front and rear axles. The main change speed gear box 119 is of the planetary type with three electromagntically actuated brakes to yield first, third and reverse speeds and an electromagneticallyactuated clutch to yield a second speed (direct drive). The ratio of the lowest speeds in the gear box 119 is the same as that of the reduction gear 120. The arrangement shown in Fig. 7 may be modified by the reduction gearing 120 and main gear box 119 being connected at either end of extensions of the engine crank shaft and the reduction gearing 120. may be eliminated by modifying the ratio of the bevel drive 40, 41 in the distributive gearing 113. The control circuit, Fig. 8. for the eight exciting windings of the distributive gears 113, 114 combine with exciting windings 1, 2, 3, R of the gear box 119 is under the control of the member 70 operating in a similar manner to that member 70 in Fig. 3 to give four forward speeds and one reverse speed for the vehicle. In low gear the low gear of the main gear box is engaged by excitation of the winding 1 and the low gears of the distributive gears 113, 114 are engaged by excitation of the windings R.L.N.S., R.L.O.S.. F.L.N.S., F.L.O.S. to give a four wheel drive. In the second gear the windings R.H.N.S., R.H.O.S., F.H.N.S., F.H.O.S. are excited to give direct drive in the gears 113, 114 with the winding 1 still excited, thus giving a four wheel drive. In the third gear there is only a rear wheel drive, the windings R.H.N.S., R.H.O.S. being still excited and the second gear in the main gear 119 being engaged by excitation of the winding 2. The fourth gear is a rear-wheel overdrive and is obtained by exciting the winding 3 of the main gear 119 with, the distributive gear 114 in high gear. The reverse gear is only a rear-wheel drive with the winding excited to give the reverse speed in the main gear 119 and the distributive gear 114 in low gear. The excitation for the distributive gears 113, 114 are varied according to engine torque through separate vacuum controlled resistors 90A, 90B. When the value of the resistors 90A 90B is zero the resistors are in step and advance with increasing vacuum until they reach a predetermined value, e.g. 35 ohms, when the resistor 90A connected to the gear 113 breaks the circuit and remains open for all higher values of vacuum.