Patent GB-689125-A (GB)
Title: Apparatus for the driving control of a motor vehicle
IPC: F16H61/02
Filed: 1950-10-31
Abstract: 689,125. Controlling vehicles. DAIMLERBENZ AKT.-GES. Oct. 31, 1950 [Oct. 31, 1949], No. 26557/50. Class 79 (v) The speed of a motor vehicle is automatically kept to a predetermined figure by means of a control device which adjusts the gear ratio, engine power and brake control to maintain such speed, notwithstanding variations in road conditions, e.g. gradient, which tend to increase or decrease the vehicle speed. The predetermined speed may be temporarily exceeded or reduced by an overriding manual control. The device, which is hydraulically actuated, comprises a control member A which is set according to the desired speed; a main control valve B which is connected to hydraulic brakes at H, to a source of fluid pressure at L, and to a source of fluid pressure which is proportional to road speed at J; a change-over device C which changes over from engine drive to engine braking; an engine speed regulator D which is connected at K to a source of fluid pressure proportional to engine speed, and which fixes the upper and lower engine operating speeds, this device being connected also at G to a hydraulically operated change gear mechanism such that when pipe line 84 is pressurised a lower gear ratio is engaged and when line 85 is pressurised a higher ratio is engaged; and a throttle-operating cylinder E, which actuates the throttle valve F. The position of the parts in Fig. 2 is appropriate to the vehicle proceeding at the predetermined speed with neither acceleration nor deceleration. The main control member B consists of slide valve 4 having a number of pistons thereon, which can slide in a cylinder having a number of ports arranged as shown. The slide valve 4 is held in equilibrium between the spring 3, connected to the control member A, and the combined pressure of spring 5 and fluid pressure at J proportional to vehicle speed. In the position shown, fluid pressure from L is communicated via 29 to pipe 35, whilst pipe 34 communicates through 21 with atmosphere. Should the vehicle speed rise through running downhill, pressure in chamber 6 is increased and the slide valve 4 raised; or should the control member A be re-set to produce higher speed, the slide valve 4 is raised. Raising of the slide valve first causes piston 13 to cut off pressure from L to pipe 35 and then vents pipe 35 to atmosphere through chamber 23, and causes pipe 34, which was previously at atmospheric pressure, to be pressurised through chamber 22 and pipe 29. The change over of pressure from 35 to 34 is communicated straight through device C to 58 and 57 and causes pressure to be removed from chamber 61 to 62 in the throttle-operating cylinder E, so causing a lowering of the piston 59, a closing of the throttle F and reduction of road speeds. The reduced speed lowers the pressure at J proportionally and so restores the balance. If the vehicle still continues to gain speed, e.g. due to the road gradient, the piston 59 moves to the bottom of cylinder 61 to close the throttle completely, and to admit pressure from the space 62 above the piston into line 90. This raises piston 39 (normally lowered) if the change-over device C, and so raises valve 38 to change-over from engine driving to engine braking. In the position shown, but with valve 4 raised due to the speed exceeding the predetermined setting, pressure from J is communicated through 28, 20, 32, 51, 83 and 79 to 85, whilst 84 is vented to atmosphere through 78, 81, 50, 33 and 21. When the valve 38 in change over device C is raised as described above, line 85 is vented to atmosphere through 79, 83, 51, 33 and 21, whereas line 84 is pressurised through 78, 82, 52, 32, 20 and 28, with the result that a lower gear is engaged to use the engine as a brake, the throttle still being closed. Should the vehicle speed continue to rise notwithstanding the closed throttle and engine-braking, increased pressure at J causes the valve 4 to rise still further until piston 8 passes pipe 31 so that pressure from J passes via 27 and 18 to hydraulic brakes at H, to reduce speed to the pre-set figure. When the vehicle speed falls, the slide valve 4 moves down below the position shown, whereupon there is first a change over to a higher gear ratio by pressure passing through 28, 20, 33, 51, 83 and 79 to 85, then the throttle valve F is opened, and if applicable the slide valve 38 in the change-over device C is moved downwardly to the engine drive position. The enginespeed regulator D is shown in its normal position. If engine speed exceeds the pre-determined maximum, the resultant pressure at K, which is proportional to engine speed, lifts the slide valve 63 against the combined action of springs 69 and 70. This disconnects pipes 84 and 85 from 81, 82 and 83 which normally control the gear ratio, and connects 85 through 79 and 88 with pressure K, whilst 84 is vented to atmosphere through 77. This causes a higher gear ratio to be engaged with consequent fall in engine speed. Conversely, a low engine speed and hence low pressure at K permits the spring 70 to lower the slide valve 63, whereby 85 is vented to atmosphere through 80 whilst 84 is connected through 88 with pressure at K. Thus a lower gear ratio is engaged with consequent increase in engine speed. The springs 69 and 70 are pre-compressed according to the setting of the control lever A so that when the control is set for a higher speed, the maximum engine speed permitted by regulator D is raised. Detail modification described include (i) an additional hydraulic control device to be inserted at H whereby the application of the brakes would be more progressive with movements of the slide valve 4, (ii) the insertion of a delaying device in the pipe 89 whereby there is a time lag between operation of the changeover device C and movements of the throttle control piston 59, and (iii) the provision of two pedals in conjunction with the control lever A, one of which temporarily reduces the pre-set speed and the other temporarily increases it. It is preferred to use an infinitely variable gear.