Patent GB-1337712-A (GB)
Title: Transmission controls
IPC: F16H61/02
Filed: 1972-04-06
Abstract: 1337712 Change speed control GENERAL MOTORS CORP 6 April 1972 [26 May 1971] 15842/72 Heading F2D Fluid-pressure-engaged ratio-selecting clutches and brakes of a four speed and reverse threetrain planet gear, e.g. on a gas-turbine driven motor vehicle, are selectively controlled by individual differentially-landed shift valves 104 .. 110, one for each ratio, actuated by solenoids D ... G, the current in which, during a shift, is modulated electronically in response to input speed, acceleration and up or down shift, to control the rate of increase or decrease of ratioengaging or release pressure. Each solenoid valve 104 ... 110 is associated with a relay valve 134...140, from which it receives its ratioengaging pressure 126, and the relay valves are fluid-interlocked so that any operative one deactivates all the others by applying pressure to end-plugs 192, 194 or the valve-spool 188 itself. Gear arrangement.-The gear is that of Specification 1,226,519, the input 10 being clutched at 54 in all forward ratios to the connected second ring 30 and third sun 26. Three reduced ratios are provided by brakes 58, 56 and 52; direct drive by a second input clutch 48 to the connected first and second suns 22, 24; and reverse by the clutch 48 and brake 58. Fluid system.-A pump 60 feeds a main 66 at a pressure level set by a regulator 72 (not described) which establishes pressure in an engaging passage 126, whilst a lower pressure, provided by a reducing valve 78, fed through a filter 74, non-return valve 76 and accumulator 80 feeds a solenoid pressure line 96, which feeds the upper chambers of solenoid shift valves 68, 70, 104, 106, 108, 110 controlling respectively neutral, forward-reverse, and the four forward ratios, the latter through relay valves 134, 136, 138, 140.  The relay valves have an interlocking action by means of two upper plugs 192, 194 and the upper spool land, each one of which receives pressure through a line connected to a brake controlled by the other shift valves, so that all relay valves not effective are downshifted to exhaust their brakes by pressure in that brake which is becoming effective. This provides a torque overlap control during shift. Solenoid shift valves 104 &c.-These each comprise a valve spool 162 shifted downwards to blank a common exhaust passage 178, and connect the first ratio brake 58 to engaging pressure 126, 182, when the solenoid D is energized to close, against spring pressure, an exhaust from the upper pressure chamber fed through a restrictor 174 by the solenoid pressure line 96, the downward movement being opposed by a spring and outlet pressure acting on differential lands of the spool. The solenoid (described in U.S.A. Specification 3,225,619) is variably energized (as described below) so that outlet pressure is regulated in accordance with solenoid current to produce a desired rate of increase and decrease of brake engaging pressure. This, together with the interlocking relay valves which control overlap, eliminates the necessity for timers and trimmer valves to control shift quality. The forward-reverse and the neutral valves 70, 68, have control solenoids C and A, B respectively, which open their pressure chambers to exhaust when energized, and close them under spring load when de-energized. The neutral valve 68 has a solenoid valve A, B at each end, the lower chamber being pressurized at 132 when the solenoid B is de-energized, to assist the spring in maintaining the upper neutral position. Solenoid B is energized when A is deenergized to shift the valve down. Action.-Initially the shift solenoids are deenergized. For a forward start the de-energized solenoid valves A and C shift down the neutral valve 68 and forward-reverse valve 70, pressurizing the engage line 126 and the forward clutch 54. On now energizing the solenoid D, the first ratio valve 104 is shifted down to supply engage pressure 126, 182 to the first ratio brake 58, a line 180 from which then acts on the upper plugs 194a &c. of the second, third and fourth relay valves 136, 138, 140 to maintain or shift them down to exhaust their shift-valve supply lines. For 1-2 shift the solenoid D is de-energized and E energized to actuate, as described for first ratio, the second ratio shift-valve 106, which receives its engaging pressure 126, 202 for the second brake 56 only after the second relay valve 136 has been permitted to be spring-returned upwards by the exhausting of the line 180 connected to the first brake 58, now exhausting through its de-energized shift-valve 104. The third ratio solenoid valve 108 acts similarly, but the fourth, 110, is inverted so that, with the solenoid G de-energized, engaging pressure 126, 206 from the fourth relay valve 140 passes through the fourth solenoid valve 110 (position shown), line 160 and forward-reverse valve 70 (in its lower position) to the direct clutch 48. The solenoid G remains energized in ratios one to three and is de-energized for four. Thus failure of solenoids D, G would cause selection of fourth ratio. For reverse the solenoid C is energized permitting the forward-reverse valve 70 to rise (position shown) exhausting the forward clutch 54 and directly pressurizing the direct-reverse clutch 48, the first shift valve 104 being energized for engaging the brake 58. A check valve 222 maintains a residual pressure (¢-¥ p.s.i.) in the common exhuast line 178. Electrical system. (1) Shift.-Energization of the solenoids D...G of the shift valves, C of the forward-reverse valve, and A, B of the neutral valve is controlled by a shift-point control 230, which may be manual or automatic as described in U.S.A. Specification 3,448,640, using as a torque demand parameter engine throttle or, in the case of a gas-turbine set, gasifier speed. From the control 230 issue a reverse signal 232 for energizing the solenoid C for reverse; a forward-enable signal 236, effective in all forward ratios and producing first ratio when alone, and second, third and fourth ratios when accompanied by respective signals 248, 250, 252. A range line 240 connected by diodes to lines 232, 236 energizes the lower neutral-valve solenoid B (to permit downward movement of the neutral valve 68), and the first ratio solenoid D, in the absence of any other ratio demand, and is connected through an inverter 244 to energize the upper neutral-valve solenoid A (to cause upward, neutralizing movement of the neutral valve 68) only when the line 240 is not energized. (2) Modulation.-Valve solenoid current (and hence ratio establishing pressure) is modulated by a computer 262, responding to signals 257 and 260, representing respectively input speed and acceleration (positive or negative), the latter obtained by differentiating the speed signal, and to upshift and downshift signals 264, 266, the computer issuing signals 268, 270 to a gate 276, controlling selectively output drivers of the first three ratio solenoids D, E and F, and similar signals 272, 274 for the fourth ratio solenoid G, the selection being made by first to fourth timing and logic circuits 280 ... 286, acting on the gate 276 through a diode matrix, and providing appropriate signals in the upshift and downshift lines 264, 266 energized by lines V1, D1 &c. of the logic circuits. During a shift, after the selected ratio has had time (two seconds) to engage fully, the effective logic circuit erases the up or downshift signal at V or D and energizes a line 292 &c. which ensures that full energization of the new ratio is completed. During every shift (except N-1 and 3-4) a timer 300 is energized through the diode matrix to cause the gate 276 to maintain the fourth ratio solenoid G fully energized (for fourth ratio release) until 0À5 second after completion of the shift, and a line 306, connected to the neutral valve solenoid A, similarly energizes the fourth solenoid G when the neutral solenoid is energized. A specimen 1-2 upshift is as follows. The energized second ratio line 248 activates the second timer and logic circuit 282, producing the upshift signal V2 for the upshift line 264. The gate 276 then energizes the second ratio solenoid E by the modulated signal 268, and connects the first ratio solenoid D to the line 270 for modulated de-energization of the releasing solenoid D. After two seconds the line 297 enforces complete energization of the second solenoid E and de-energization of the first D.