Patent GB-740985-A (GB)
Title: Improvements relating to automatic gear-change arrangements for change-speed gearing
IPC: F16H61/02
Filed: 1952-12-22
Abstract: 740,985. Change-speed gear. DAIMLER-BENZ AKT.-GES. Dec. 22, 1952 [Dec. 20, 1951; Dec. 8, 1952], No. 32527/52. Class 80(2) [Also in Group XXIX] A four-speed gear on a motor - vehicle controlled automatically in response to vehicle speed and torque, as represented by engine manifold depression or fuel - injection pump setting, together with accelerator kickdown shift, is subjected to a driver - operated control providing three ranges of operation, permitting respectitvely the use of all four ratios in a "Normal" range, the first three only in a "Braking I" range, and the first two only in a "Braking II" range, and has limiting speeds for the ratios so selected as to divide operation into a number of speed-zones e.g. O-V1; V1-V2; V2-V3, Fig. 1, in each of which zones only two ratios can be engaged, so that the maximum speed for one ratio (e.g. V1 for first) is equal to the minimum for the next higher but one (e.g. third). The invention is directed to the inter-action between an output-driven governor-valve R, a manual range-selector valve Q, and an excess pressure valve U in the fluid-pressure control of the gear to produce the above result. Function summary. Fig. 1 shows the shiftpattern in "Normal" range, the maximum power curves for the respective four ratios (which are in geometrical progression) being N1, N2, N3 and N4. In this range the power peaks of the first and second ratios are not used, the 1-2. 2-3 and matically at the points A, F, K respectively 3-4 upshifts being arranged to occur autoin response to vehicle speed alone as the upper speed limits V1, V2, or V3 are exceeded in any particular zone whilst working in the lower speed ratio of that zone. The .dotted upshift line GO including the points A, F, K is chosen as a load-line of constant manifold depression or fuel-injection pump setting on which the noise level of the engine does not exceed that of the vehicle. The speed responsive control acts in steps corresponding to the zones, its effect being held constant in each zone so that with the speed limits of any one zone (e.g. V2-V3), upshift from the lower (third) to the higher (fourth) of its two ratios occurs automatically due only to reduction in load (as manifested by increased manifold depression), whilst the corresponding downshift (4-3) occurs only at the driver's will by accelerator kickdown. Thus on full throttle in zone (1), O-V1, full load upshift from first speed occurs at A to second speed at B; and under light load at A1 to B1, whilst the part-throttle curve N1<SP>1</SP> would give full load upshift at A' to B. If the low-speed line under light load e.g. N1<SP>11</SP> is so low as to intersect the second speed line N2 e.g. at B<SP>1</SP>, upshift occurs at that point. Operation in first speed in zone (1) is thus restricted to within the area OAB, second speed being automatically engaged in response to load within area OBC. In zone (2), V1-V2, operation in second speed is similarly restricted to an area BFED between second and third speed lines N2 N3, third being introduced in the underlying area CDEG, and in zone (3), V2-V3, third speed in area EKJH and fourth in GHJV3, followed by the fourth zone V3- V4, permitting use of' fourth speed only. Speed-responsive downshifts on passing from one speed zone to the next lower zone occur automatically at correspondingly lower speeds V1<SP>1</SP>, V2<SP>1</SP>, V3<SP>1</SP>. The "Braking 1" range (Fig. 2, not shown) is similar except for the omission of the fourth speed curve N4 and an increase in the upper limit of speed for zone (2) from V2 to a higher speed, which includes the peak of the second speed curve N2; whilst in "Braking 2" range (Fig. 3, not shown) only the first and second speed curves N1, N2 appear and the shift occurs over the peak of the first speed curve N1 at the upper limit V2 the single zone being now O-V2. Within each zone a downshift can only be made at any time by accelerator kickdown there being no load-responsive downshift. In the braking settings downshifts which might result in excessive engine speed are prevented. As shown, in zone (1) the commencing limit for the second speed line N2 is extended back to O, so that in all settings starts are always made in second speed, first being introduced by accelerator kickdown only, automatic speed-responsive downshift on entering zone 1 being suppressed. Gear arrangement. In Figs. 14-16 three countershaft reduced ratios and reverse pass through a fluid coupling 202 which is mechanically bridged (and emptied) for fourth speed, direct-drive, by a friction clutch 210. The gear-ratios are in geometric progression. An input member 202 carries the impeller of the coupling, the turbine 208 of which is fast through a sleeve with a wheel 214 driving a countershaft 216. to which can be frictionally clutched at 222. 223, second and third speed wheels 220, 221, meshing wheels fast on a final output shaft 217, 227. Dog-clutchable to the output shaft 227 is a free-wheel mounted low speed wheel 228 paired with a countershaft wheel 226 behid the rear wall 224 of the gear case. The low-speed wheel 228 may remain clutched in, and overrun after engagement of higher speeds. A reverse idler shaft 229, Fig. 15, has fast and clutchable wheels 231, 232, the former meshing the countershaft wheel 221, reverse path being from countershaft 216 through wheels 226, 228, 232, 231, 221 and 219, to the output shaft 227. The disc clutches 222, 223, 210 and the dog-clutch 228 of second, third, fourth and first speeds respectively are hydraulically actuated through a valving control arranged in two transverse units in a chamber 213 between the fluid coupling and the gear. Clutching pressure is varied to suit the load under control of engine-manifold depression as described below. Pressure supply system. Input and output driven pumps P1, P2, Fig. 5, supply pressure oil to the servo-system through a double check valve V of the ball or disc type which closes to that pump producing the lower pressure. The vehiclespeed responsive pressure for the automatic control is supplied by a smaller separate pump P feeding a governor valve R which varies the pressure in steps corresponding to the speed limits of the ranges, as described below. The input pump Pl is coaxial with the main shaft 227, Fig. 14, arranged in the chamber 213 and driven by a sleeve 205 fast to the main input member 202. The output pump P2 and governor-supply pump P are arranged sideby-side in a casing 234, Figs. 15 and 20 (the latter shows a modified valve construction), and driven, jointly with the governorvalve R by the reverse idler shaft 229 which is driven by the output shaft 227. A pneumatic system may replace the hydraulic one described. Fluid system components. The second, third and fourth speed clutches II, III and IV are fed through shift valves S2, S3, S4, with pressure supplied to delivery lines 130, 131, 129 respectively of a pressure-regulating valve T the lands of which are staggered to supply the lines in sequence in the order named, whereby loss of pressure due to opening the line to a clutch to be newly engaged during a gear shift causes immediate throttling of that line and avoids loss of pressure in the line of the superseded clutch, as described in Specification 737,319. A line 132 leading from the regulator T to a lubrication main lub and, through 136, to the fluid-croupling Hy is opened by the regulator T last of all. The regulator T is loaded rightwards at 122 by pressure from the pump main 107, 120 which includes a filter 108, and also by engine manifold depression at 97 acting on the right side of a diaphragm M. Leftward force is provided by a valve-stem spring 93 and a diaphragm-loading spring 98, which, when the accelerator-pedal 100 is depressed beyond full-throttle (shown), is acted on by a stem 99 to increase leftward loading for kickdown shift. The shift-valves S2, S3 are fluid-actuated through relay valves K2, K3, whilst the shift-valve S4 is directly fluidactuated, these three valves K2 K3 S4 being subjected on their opposite faces to pressures responsive respectively to vehicle-speed and engine manifold depression to produce the automatic shifts. The regulator line 129 supplying the fourth speed valve S4 also feeds directly the first speed clutch I. A four-position range-selecting valve Q is actuated by a lever 16 linked to a gate-guided manual range-shift, reverse, neutral and park-lock lever (see below) and is in two rigidly-connected sections, the lower section Q2 serving to exhaust all the shift-valves in neutral; permit all to be effective in "Normal"; exhaust the fourth speed shift valve S4 in "Braking I"; and exhaust also the third speed shiftrelay valve K3 in "Braking II". The upper section Q1 of the ranging valve co-operates with the governor valve R to produce the required pressure changes for the different ranges. A valve Av unloads the input pump P1 at 142 when regulated pressure in the fluid-coupling feed-line 136, acting at 139, reaches a predetermined value and also relieves excess regulated pressure at 141. Governor valve. The governor-valve R cooperates with a spring-loaded relief valve U and the upper section Q1 of the ranging- valve to provide four distinct and constant pressures P1, P2, P3, P4, Fig. 7; corresponding to the various speed zones shown in Fig. 1 for "Normal"; three pressures P1, P2, P3 for the "Braking I" range, and two, P1, P2, the latter commencing at V2 for the "Braking II" range. The governor valve. R, Figs. 5 and 6, comprises a rotating body R fast on a stem 34 driven proportional to vehicle speed through the reverse idler shaft 229, Fig. 15, and having four radial chambers 43, 44, 45, 46, connected by axial bores , 39...42 with grooves 35...38 respectively in the stem 34, to which grooves pressure-oil is supplied by the separate vehicle-driven pump P through the relief valve U and ranging