Patent GB-1423940-A (GB)
Title: Power trains utilising gas turbine engines
IPC: F02C9/00
Filed: 1974-05-23
Abstract: 1423940 Gas turbine plant GENERAL MOTORS CORP 23 May 1974 [2 July 1973]  23111/74 Heading F1C [Also in Division F2] A power-plant for driving a motor vehicle  comprises a gas turbine, including a gas generator (turbine 14 driving a centrifugal compressor 11), and a power turbine 17 driving the load 25 through a variable ratio transmission 20 having ratio establishing devices, established under control of a manual selector valve 125 by fluid-pressure from a pump 41 driven by the engine and also having fluid connection to the power-plant control; and overcontrol means connected to the ratio selector and to the power-plant control operable in a ratio  established condition to control power-plant output, and in neutral N to disable the supply of fluid-pressure from the pump 41 to the power-  plant control to reduce power-plant output. General arrangement. In the turbine plant shown, output is controlled not only by the manual control lever 26 (accelerator pedal) operating the fuel control 23, but also by a power transfer clutch (PT clutch) 44, transmitting torque mechanically and variably in either direction between a shaft 37 gear-driven by the gas generator shaft 14, and a shaft 45 similarly geared to the shaft 18 of the load turbine 17, the amount of power thereby transferred for driving or braking the final output 18 being varied by variably controlling the slip in  the PT clutch 44 by varying the fluid-pressure engaging load applied to it by the pump 41.  Fluid-pressure supply. The pump 41, driven, along with engine auxiliaries 40, by the gas generator shaft 37, supplies pressure, regulated at 53 to a constant intermediate value (120 p.s.i.) to a line 58, providing the source for engaging the PT clutch 44, and also the input to a second pump 43, driven either by the gas generator or turbine shafts 37, 45, and regulated at 96 to a constant high pressure (230 p.s.i.) supplying a line 93 serving the ratio selectors of the transmission 20. Spill from the regulators passes to restricted lubrication lines 57, 164, and during neutral a lowest pressure (60 p.s.i.) is established in the lubrication line 164, for which see below. Engine starting. Following closure of a key switch 142 an electric starter motor 149, for turning the gas generator shaft 14, is energized by closure of a manual switch 146 arid lower contacts of a switch 148 closed by a cam 152 on the ratio selector valve 125 in its neutral N setting only. Completion of the starter circuit also energizes a solenoid valve 157 which vents the suction line of the first pump 41, thus ensuring release of the PT clutch 44 and relieving the gas generator of all load. Neutral. Upper contacts 15 1 of the neutral switch 148 energize a delay action relay 172, which energizes a solenoid 183 controlling a  throttle back-stop for the manual fuel control 26 to establish a lower idle speed of the engine in neutral than in any running ratio, when the solenoid 183 is de-energized. The relay 172 also energizes a solenoid valve 158 opening a pressure line from the pump 43 through a one-way valve 163 to the lubrication line 164 and through a restrictor 161 to exhaust, to stabilize a low-pressure (60 p.s.i.) in the lubricating line 164 in N setting.  PT clutch 44 is a multi-plate friction clutch the torque capacity of which is variably controlled by variable hydraulic pressure applied to two separate cylinders containing a single stepped piston, one cylinder receiving pressure from a power load line 49, the other from a brake load line 50, and of greater area, to establish a brake torque capacity much (five times) greater on brake than on power, to brake the output by compressor load on overrun. The clutch is cooled by spill 54, 56 from the regulator 53, returning to exhaust through a line 77.  PT clutch control. Hydraulic clutch-engaging pressure is controlled jointly by a torque sensor 61, responding to torque transmitted through the gear train 35 by the gas generator shaft 14 to the input shaft 37 of the PT clutch 44; a speed transducer 39 driven by the same shaft 37 and producing a speed signal pressure 67; and a torque programmer 66, which receives regulated pump pressure 58 and issues therefrom a power signal pressure to a line 68, 73 in accordance with'the speed and torque signals 67, 62, the latter received from the torque sensor 61, which receives regulated pump pressure 58 and issues also brake signal pressure 63, communicating directly with the clutch brake line 50. During power drive the torque sensor 61 exhausts the brake signal line 63 at 64, and the torque programmer 66 compares the measured torque and speed signals 62, 67 with a desired  power transfer signal and issues a resulting pressure signal through the power signal line 68, 73 to the clutch power load line 49 to modulate clutch capacity accordingly. Torque reversal causes the torque sensor 61 to exhaust the power signal 62 at 64, whereupon the torque programmer 66 applies full regulated pump pressure 58 through the power signal line 73 to the clutch power line 49, whilst the torque sensor 61 also applies the same pressure 58 directly to the clutch brake line 50, so that the power and brake pistons together load the clutch 44 to maximum pressure for non-slip over-run braking. Modulating the PT clutch engaging pressure are an acceleration valve 69 and temperature valves 76, 81. The acceleration valve 69 is actuated mechanically by substantial depression of the accelerator pedal 26, but not by small or slow depression thereof, to exhaust the clutch power signal line 73, thus releasing the PT clutch 44 and unloading the gas generator to permit more rapid acceleration thereof. An over temperature valve 76 also relieves PT clutch power or brake pressure in response to excessive temperature of the exit cooling oil 77, by closing the power and brake lines 49, 50. A temperature compensating valve 81 bleeds pressure from the torque sensor power signal line 62 at higher ambient or engine inlet temperatures. Transmission control. Fluid-pressure for the, transmission control is taken from the high pressure pump 43, regulated at 96, to the constant pressure line 93. Included in the control circuit are a flow valve 97 and cut-off valve 111 which serve to disengage the PT clutch 44 during each ratio shift interval. For this purpose the lower end of the flow valve 97 has a restrictor 105 through which pump pressure 93 feeds the ratio selector valve line 106, and, during a ratio shift, flow in the line 93, 106 creates a pressure drop across the restrictor 105 resulting in raising the spool of the flow valve 97 to exhaust a line 101, thereby permitting a spring to shift rightwards the spool of the cut-off valve 111, which exhausts both power and brake lines 49, 50 of the PT clutch 44, causing release thereof. With cessation of flow on shift completion the valves 97, 111 return to the positions shown, closing the exhaust and thus restoring clutch pressure, a delay time being imposed by a restrictor 108. In neutral setting N, the low-pressure (60 p.s.i.) established in the pump output line (see fluidpressure supply above), is insufficient to keep the cut-off valve 111 in the closed position shown, and this valve opens to release the PT clutch 44. During a subsequent shift from N to a ratio setting, the time delay relay 172, capacitor controlled, keeps the PT clutch 44 released for a predetermined time to produce a smooth shift. Engine fuel supply. The gas generator is supplied with fuel through a line 29 by a circulating pump 24 driven by the gas generator shaft 37, the fuel quantity being controlled by the manual accelerator 26; speed responsive pressure 48 supplied by a governor 47 e.g. of the pitot type, driven by the turbine shaft 18; speed responsive pressure 67 from the transducer 39 driven by the gas generator shaft 37; and compressor delivery pressure 31. None of the individual items shown is described in detail, but references are made to various U.S.A. Specifications for items such as the torque sensor, torque programmer, clutch, governor &c.