Patent GB-798559-A (GB)
Title: Improvements in or relating to transmission mechanism
Inventor: SMIRL RICHARD L
IPC: F15B21/045
Filed: 1955-10-31
Abstract: 798,559. Change-speed gear. BORGWARNER CORPORATION. Oct. 31, 1955, No. 31054/55. Class 80 (2). In a planetary change-speed gear having a power-train-completing friction engaging device such as a clutch C1, C2 or brake 20, 21, the said device is engaged by liquid pressure increasing with the speed of one of the shafts of the gear, and provided by a pump 90, driven by that shaft and having in its intake a viscous restrictor such as a fine mesh screen 106 of considerable area, a streamlined body or a number of closely spaced parallel plates, and in its delivery 99 a sharp edged orifice 124 in a thin plate, promoting turbulence. By these means it is ensured that delivery pressure is proportional to speed independently of changes in liquid viscosity due to temperature, although an additional temperature-responsive control, described below, is also provided. Function summary.-Nested input clutches C1, C2 of a planetary gear are engaged by fluid pressure which is input speed responsive up to clutch engagement speed for automatic start in any ratio, clutch and brake pressure being thereafter responsive to engine manifold depression only. Three constructions are described, all having three forward speeds, first being one- or two-way, reverse and tow-start (in direct drive). In the first construction shift is by manual selector valves 163, 164 only. The second, Fig. 14 (not shown), provides in addition a 1-2 upshift by an automatic shift valve operated by opposing fluid pressures responsive respectively to manifold depression and output speed; 2-3 manual upshift and similar automatic 3-1 downshift. The third construction adds to the second, automatic 2-3 and 3-2 shifts responsive only to output speed, with 3-2 accelerator kickdown shift, both acting electrically on the manual selector valves. Gear arrangement.-Intermeshed planets on a free carrier mesh an output ring 50 fast on an output shaft 17, and suns 51, 54 on concentric shafts 14, 15 selectively clutched to an input flywheel 12 by disc clutches C1, C2, engaged by supplying pressure fluid to pistons 40, 41 connected rigidly to respective presser plates 27, 30. First speed is by engaging the clutch C1 to drive the sun 51, and the planet carrier reacts on a oneway detent 19 for one-way drive, or on a bandbrake 21 which is applied for two-way drive. Second speed is by braking the sun 54 at 20, using the clutch C1 as in low, the detent 19 overrunning. Third speed, direct drive is by engaging both clutches C1 C2 together. Reverse is by engaging the clutch C2 to drive the sun 54, and brake 21 to hold the planet carrier. For smooth engagement, oil is supplied to both clutch discs from a relief line 127 of the fluid system arranged near the shaft axis. The gear is lubricated from a restricted relief line 203 fed by an output driven pump 91 of the system. Fluid supply and control.-Input and output driven pumps 90, 91 supply pressure fluid to the clutch and brake-engaging pistons under control of two selector valves 163, 164 operated simultaneously through a common lever 175 by a manual lever 176 having seven positions as follows. In neutral, pressure is supplied only to the brake 21 used in reverse and two-way low; in one-way low, to the clutch C1 only; in second (position shown), to the clutch C1 and brake 20; in third, to both clutches C1 C2; in reverse, to the clutch C2 and brake 21; in two-way low, to the clutch C1 and brake 21; and in tow-start to both clutches C1 C2 together as in third, but with different pressure conditions. Starts are made in any ratio, the brake (where required) engaging first and the clutch having graduated engagement for automatically taking up drive. Pressure control.-To provide for automatically engaging the clutch or clutches for starting the vehicle, input pump delivery,pressure 99 is required to be speed responsive independently of temperature, for which purpose the pump intake 98 has a fine-mesh screen 106 of large area, causing viscous resistance, and the delivery 99 has a relief 127 through a sharpedged orifice 124 in a thin plate to cause turbulent resistance. The orifice 124 is varied by a plunger 129 controlled by a thermostat spiral 134 which turns the eccentric fulcrum of a lever 130 carrying the plunger at one end and adjusted also at the other end as described later. Delivery pressure 99 is required to be speed responsive only up to the complete engagement of the starting clutch, after which pressure is relieved through a valve 107 loaded by a spring-loaded diaphragm 114 subject at 113 to engine-manifold depression up to a limit set by a spring- loaded ball relief valve 120. Thus, after clutch engagement, input pump delivery pressure 99 increases automatically with increased torque as manifested by increased manifold pressure. Additional control over the speed-responsive pressure range only is provided by abutment of the selector-valve 163 on an adjustable screw 182 in the free end of the plunger lever 130. In first speed the selector valve 163 is clear of the lever 130 which is spring-loaded on to an adjustable stop 183; in second, the selector valve contacts and raises the lever end 182, to reduce the orifice 124 thus increasing pressure; in third the valve moves further in the same direction but the orifice 124 still remains large enough for the vehicle to be stopped without stalling the engine; whilst in tow-start the valve completely closes the orifice 124 if the oil is warm. Stall speeds in first, second and third speeds are thereby arranged to be 750, 1000 and 1250 R.P.M. respectively, and the vehicle can be started in any ratio. Pressure for the rear clutch C2 is also subject to a further reducing control in third speed setting only, in which ratio the planet gear determines that that clutch C2 carries only onethird input torque. For this purpose the clutch C2, in third speed only, takes its pressure from a line 187 supplied from the pump delivery 99 at a lower pressure through a differentiallylanded reducing valve 188. Engagement of the second-speed brake 20 is cushioned by a restrictor 156 and accumulator 157. Fluid fed through the relief line 127 to the clutches C1, C2 passes radially out through inclined radial grooves in the friction facings into the clutch housing, where it is picked up by the toothed flywheel 12 and fed through a channel, Figs. 3 and 4 (not shown), to a main reservoir 104. In Figs. 14 and 16 (not shown) the fine-mesh pump-intake screens 106 are replaced respectively by an elongated streamlined body and by closelyspaced parallel plates inside the intakes. Automatic shift.-Fig. 14 (not shown) provides automatic shift from first to second speed by a shift valve between the selector valve block and the second-speed brake line 151, such valve being subject on one face to spring and input pump pressure, which, above a predetermined engine speed, is responsive to enginemanifold depression (and hence is " TV " pressure) and on its other face to parabolicallyvaried output-speed responsive pressure of the output-pump delivery line 103 which now has a sharp-edged relief orifice with thermostat control like that 124, 134 of Fig. 6. A spring- loaded ball valve connects deliveries of output and input pumps, but is only opened at above 45 m.p.h. by output pump pressure, whereafter both pressures are equalized. Starts are made with the manual shift-lever set in second speed, but the automatic shift valve blocks supply to the second speed brake 20 so that start is in first speed, until output-speed-responsive pressure prevails over TV pressure to open the automatic shift valve and apply the brake 20 for 1-2 upshift. Shift to third is by the manual lever only, and when, on reducing output speed, TV pressure prevails over speed-responsive pressure (which, due to differential shift-valve lands, is at a lower speed than for the reverse movement) the automatic shift valve downshifts by exhausting the brake 20, input pump pressure is also applied to a piston which returns the manual shift lever to low, so that the resulting downshift is 3-1. Automatic and kickdown shifts.-In Fig. 16 (not shown) the piston control of the manual shift lever producing the 3-1 downshift as above is replaced by a solenoid energized only below a predetermined output-speed-responsive pressure by a switch operated by a Bourdon tube, and also energized by an accelerator kickdown switch. After automatic 1-2 upshift by the automatic valve as above described, the manual shift lever can only be moved to third speed above the predetermined output speed, and subsequently on decelerating below that speed, or on accelerator kickdown, a 3-2 downshift occurs, followed later by a shiftvalve 2-1 downshift as above described. The coiled thermostat control of output speed responsive pressure like that 124, 134 of Fig. 2, is replaced by a flat-bi-metal strip carrying a taper plug projecting into an orifice in the wall of the delivery conduit.