Patent GB-1231821-A (GB)
IPC: F16H59/38
Filed: 1968-05-16
Abstract: 1,231,821. Variable-ratio transmissions. TOYOTA JIDOSHA KOGYO K.K., and AISHIN SEIKI K.K. 16 May, 1968, No. 23439/68. Heading F2D. A transmission comprising a hydrodynamic torque converter followed by a three speed and reverse bevel epicyclic gear has shifts between second and third ratio in the epicyclic gear controlled automatically in accordance with the dynamic pressure or circulating flow speed of fluid in the converter. The transmission has a wholly manual first ratio and wholly automatic shifts from second to third ratio. Gearing.-As shown a torque converter has one-way mounted stator 12 and a turbine 7 carrying a pitot tube 8 for measuring the pressure of the fluid. In a modification (Figs. 7-10, not shown) a second pitot tube is carried by the impeller for measuring the pressure during braking to provide automatic downshift to second under these conditions. The turbine shaft 7a can be connected by a clutch 15 to a shaft 16 carrying a bevel sun gear 17 and can be connected by a clutch 18 to a bevel sun 22 which can be stationed by a brake 20. A tilted planet 23 meshes the suns 17, 22 and is fast with a planet 24 meshing an output sun gear 25. The planet carrier is connected to a stationary housing by a one-way brake 30 and can be stationed by a brake 29. A parking brake 31 is provided on the output shaft. Control.-Pressure from the pitot 8 is supplied (or in the form having two pitots the operative pitot is connected through a shuttle valve) through a line 8c to a chamber 35c to bias a main regulating valve 35 downwardly and is also supplied to a chamber 70 of a two-three shift valve 71. An input driven pump 6 is connected to a chamber 35d of the regulating valve which adjustably partially covers an exhaust passage 34 to regulate the pressure in the chamber 35d. The regulated pressure in chamber 35d is supplied through a passage 41b to control valves and thence to the clutch and brake servos, and is also supplied through a passage 41a to a valve 40 which is spring biased to give a constant pressure in a line 42 which supplies fluid to the torque converter and is also connected to a chamber 35c to bias the valve 35 in opposition to the pitot pressure to substantially eliminate the effect of the static pressure in the torque converter on the regulating valve. The chamber 34e is connected through a restrictor 42c to an output driven governor valve 32 which provides a pressure proportional to the output speed in a line 42d leading to a chamber 70a of the twothree shift valve. A manual shift valve 56 has positions DLNRP corresponding to drive, low (first ratio), neutral, reverse and park, and controls the supply of regulated pressure 41b to lines 61a-64a leading respectively to servos for applying the brake 20, clutch 15, brake 29 and clutch 18. The valve 56 also controls the supply of fluid controlling a valve 66 which is thereby actuated to cut off the two-three shift valve from the clutch and brake servos in all positions of the manual valve 56 except drive and park. Operation.-Manual valve 56 in D position. As shown in Figs. 3-5 the second ratio is engaged, regulated pressure being supplied to engage the clutch 15 and the brake 20. With increasing output speed and decreasing pressure in the torque converter the two-three shift valve 71 is moved to the right by governor and spring pressure acting against the pitot pressure and the servo of the brake 20 is exhausted and clutch 18 applied by way of the line 65a to give third ratio. In the position L of the valve 56 the clutch 20 is engaged and brake 29 applied to give first ratio; in position N both clutches are disengaged; brake 29 is applied but this is immaterial. In position R, clutch 18 and brake 29 are applied. In order to cushion shifts needle valves 75, 80, 85 are provided in passages leading to the brake and clutch 18 servos and are loaded when the clutch 15 is engaged to delay engagement of the respective brakes and the clutch 18. By-pass valves ensure rapid disengagement of the brakes and this clutch. Modifications.-In a modification the governor pressure is responsive to input speed instead of to output speed, and in a further modification the governor pressure loading of the two-three shift valve is replaced by accelerator position responsive loading. In yet another modification the regulator valve 35 is dispensed with, the clutch and brake servos being supplied with the pitot pressure.