Patent GB-1232131-A (GB)
IPC: F16H61/02
Filed: 1969-01-30
Abstract: 1,232,131. Change-speed gear and control. GENERAL MOTORS CORP. 30 Jan., 1969 [5 Feb., 1968], No. 5184/69. Headings F2D and F2L. A pressure-reducing valve 188, shown as applied to a clutch-like control of a manually selected eight speeds and four reverse planetary transmission on a vehicle, is adapted to provide output pressure 191 which varies linearly in two stages (Fig. 2, not shown) with the axial position of a manually-moved control plunger 200, with which co-operates a biasing member 202 to produce a pressure-regulating action under spring loading determined by plunger position as detailed below. Function summary.-Selection amongst the five friction brakes and two clutches of the eight speed, four reverse gear is by a stepwise axially-moved manual selector valve 72 only, the valve establishing shift by fluid actuation of five separate shift valves 109, 107, 105, 233 and 172. Graduated start engagement is provided by the manual engagement control, valve 188, whilst engaging pressure rise during a shift is controlled by three separate trimmer valves 149, 168, 246. Gear arrangement.-In series ahead of a splitter unit 15 and reverse unit 16 is a four speed accelerated train unit 11, wherein a ring gear 21 of a basic train, having an input sun 19 and output carrier 24, is held for lowest speed by a brake 22, and accelerated in stages for two higher speeds by trains 13, 14, having common suns on an input shaft 17 and ring-gears held by second and third speed brakes 22a, 22b, a lock-up clutch 26 providing direct drive. The splitter unit 15 is a simple three-element train with input sun 28 driven by the preceding planet-carrier 24, output carrier 34, direct-drive clutch 33 and reduced drive brake 32 for the ring gear 11. The reverse train 16 compounds with the splitter 15, having common planet carriers 34, 43 on the output shaft 18 connected front ring 31 and second sun 38, and second ring 41 braked at 42 for reverse. Shift sequence is 1, 2, 3 in the main unit 11, with splitter in low; 4 with main unit in 1, splitter in high; 5 with main unit in direct drive, splitter downshifted to low; 6, with main unit downshifted to second, splitter upshifted to high; 7, main unit upshifted to third, splitter still in high; 8, main unit in direct-drive, splitter in high. The four reverses are all in the main gear, the compounded splitter and reverse units being in reverse. Fluid supply and regulation.-A single enginedriven pump 51 supplies a pressure-regulator valve 53, loaded by a spring, with pressure augmentation in all ratio settings except neutral through a line 184. System supply is by main 71. Pressures are specified. Manual selector valve 72.-An axially movable actuating plunger 73 is retained in thirteen positions by ball detents 81, Main pressure 71 is supplied to a space between lands 76, 77 and reaches a closed space 84 inside the plunger through a radial bore 83. An oblique bore 85 from the space 84 provides a pressure port in a grooved land 86 on the plunger 73, and a parallel oblique bore 103 provides communication to exhaust 101a from a space between lands 76, 86. Axially distributed ports lead to the various shift circuits. Shift valves.-These are relay valves which, on receipt of a pressure signal from the manual selector valve 72, are moved axially from a spring-biased unshifted position to a shifted position in which they supply pressure fluid to the corresponding ratio clutch and/or brake. Five shift-valves, as follows control all ratios. A 1-2 shift valve in its upper unshifted position supplies pressure to the first speed brake 22, and in its lower (shifted) position, to the second speed brake 22a. A 3-shift valve 107 supplies only in its lower (shifted) position the third speed brake 22b; a 4-shift-valve 105 the lock-up clutch 25; a splitter shift valve 233 supplies the splitter low brake 32 in its upper (unshifted) position and the high clutch 33 in its lower position; whilst a reverse shift-valve 172 supplies the reverse brake 42 in its lower (shifted) position. All the shift-valves are equally landed. The first three shift valves 109, 107, 105 are all similar and are each moved to their lower (shifted) position, against spring bias, by any one of three pressure signals from the manual selector valve 72 to between or above plugs 115, 116, 117 (in the case of the 1-2 valve 109). Single signals shift the remaining valves. The shift-valves 108, 107, 105 of the range unit are supplied with ratio-feed pressure through a series line 106, 108, passing from one valve to the next in descending order, so that, on upshift of one valve, the preceding lower valve is cut off from fluid supply and hence disengages its ratio. Trimmer valves.-These all have a similar action in regulating engaging pressure during shift. Taking the third speed trimmer 168, pressure in the third speed brake engaging line 144 raises, against a spring 155a, an assembly comprising a one-way poppet valve 156a, 158a and sliding plug 153a, the former opening an exhaust port 166a, for initial regulation of brakeengaging pressure 144 at a low level. Brake pressure 144, passing through a restrictor 163a in the one way valve 158a, builds up in the plug 153a, raising the latter to increase regulator loading, and hence brake pressure, until the plug 153a contacts a stop 165a, further pressure increase then shifting the one-way valve member 156a down, to close the exhaust 166a and permit brake pressure to rise to system maximum. On pressure release, the one-way valve 158a opens for rapid exhaust of the space in the plug 153a. The 1-2 and splitter trimmers 149 and 246, are both used in the control of rotating clutches and large brakes subject to higher leakage rates than the others, and these trimmers have an additional connection to main pressure, e.g. at 71 for trimmer 149, which, in the upper position of the plug 153, provides an additional pressure supply to the ratio feed line, e.g. 108, through the one-way valve 158. Restrictors 169, 171 are provided in the feed lines 108, 144 of the trimmers 149, 168, so that, during an engagement shift, rapid loss of pressure will be caused initially by the flow requirement, permitting the trimmer spring 155 to eject the small internal volume of liquid through the one-way valve 158 prior to trimming action. Engagement control valve 188, forming the main subject-matter of the invention, can be used like a clutch control, and causes system pressure to be regulated to zero in accordance with the axial withdrawal movement of a control plunger 200. The valve 188 takes in system pressure at 184 supplied from the manual selector valve 72 through the reverse shift-valve 172, and feeds a delivery passage 191 leading through the reverse and splitter shift valves 172, 233 to the reverse brake 42, or the splitter clutcn or brake 33, 32, according to shift-valve setting. As shown, in an equivalent "clutch-engaged" position, the delivery and supply passages 191, 184 are in unrestricted communication between differential lands of a regulator spool 202, pressed by springs 208, 222, 223 against an upper stop 217, and the spool 202 is hydraulically balanced by delivery pressure 191 reading its underface through a restrictor 225 and port 219. Depression of a clutch-like pedal draws downwardly the control plunger 200, separating it from the regulator spool 202 at a valve seating surface s, and also removing the load of the spring 208 from the regulator spool. Opening the valve s exhausts the underface of the spool 2C2 through an inner stop-tube 204 and exhaust port 224. The upper land of the regulator spool 202 now regulates supply pressure 184 to exhaust 224 under the loading of the two remaining springs 222, 223, which abut a collar 211 pinned to the control plunger 200, so that the spring extension, and hence the regulated pressure reduction rate are directly proportional to the axial movement of the control plunger 200. The inner spring 223 is arranged to become fully extended at about mid travel of the plunger 200, after which the spring 222 acts alone, giving a two-rate pressure-displacement line with a final part less steep than the initial, and terminating in zero pressure, free exhaust, when a stop 205 on the end of the inner tube 204 contacts a shoulder in the regulator spool 202, whereafter the spool 202 moves with the control plunger 200 to open supply 184 directly to exhaust 224, effectively de-clutching the transmission. Pressure increase, for clutching at start occurs similarly by upward movement of the plunger 200. During start, the engagement control valve 188 controls splitter and reverse pressure for a smooth start, but splitter pressure rise is still subject to automatic control by the splitter trimmer valve 233, should the operator move the engagement control valve 188 or the selector valve 72 too rapidly. The pressure passage 184 feeding the engagement control valve 188 is pressurized by either a reverse signal 178 or any forward ratio signal 179, according to the setting of the reverse shift valve 172 by the signal received from the manual selector valve 72, so that the engagement control valve 188 is effective for forward and reverse. Neutral.-In neutral the line 184 feeding the splitter and reverse units and the engagement control valve 188 is exhausted through the unshifted reverse valve 172 and the manual selector valve 72. The splitter valve 233 remains unshifted in low but the unit is not pressurized. Pressure is supplied to engage the low brake 22 of the ranging unit and system pressure is reduced due to absence of augmenting pressure 184 on the main regulator valve 53. Controlled exhaust.-A general exhaust line 137, serving the shift valves, exhausts through a spring-loaded check valve 138 which maintains a low pressure level sufficient to keep the ratio supply passages filled.