Patent GB-1445378-A (GB)
Title: Creep preventing hydraulic control circuit for vehicle automatic transmission
IPC: F16H61/02
Filed: 1973-10-24
Abstract: 1445378 Change-speed gear control NISSAN JIDOSHA KK 24 Oct 1973 [2 Nov 1972] 49498/73 Heading F2D An automatic hydraulically controlled transmission for vehicles having a plurality of shift valves controlling friction elements, i.e. clutches and brakes, to establish various gear ratios includes "creep" preventing means responsive to the positions of a ratio selector and of the vehicle engine throttle so that in certain circumstances, e.g. when the throttle is closed and the selector is in the D position, the transmission is shifted automatically into its highest ratio. Gear arrangement.-An engine driven torque converter 2, Fig. 1, drives a shaft 20 carrying elements 24, 23 of clutches 4, 5. The driven elements 29 of the clutch 4 are connected by a brake drum 30 surrounded by a band brake 12 with the suns 6c, 7c of first and second planetary trains, and the driven elements 28 of the clutch 5 are connected with ring gear 6a of the first train. The planet carrier 6b and the ring gear 7a are connected to the output shaft 15, and the planet carrier 7b is connected by a member incorporating a friction brake 9 and a one-way brake 33 with the planet carrier 8b of a third planetary train of which the sun 8c rotates with the output shaft and the ring gear 8a is connected with a friction brake 10 and a combined one-way clutch 14 and friction brake 11. In the automatic or D range, low ratio is effective with the clutch 5 engaged and reaction being taken by the one-way brake 33, and second ratio with the clutch 5 and brake 11 engaged and reaction taken by the one-way clutch 14. Engine braking is not available in these ratios. Third ratio requires engagement of the clutch 5 and brake 12, and fourth or direct drive requires both clutches 4, 5 to be engaged. The selector also has positions 1, 2, 3, to hold first, second and third ratio, the brakes 9, 10 being engaged for first and second respectively to provide engine braking, and a reverse position in which the clutch 4 and brake 9 are engaged. Hydraulic control circuit.-A pump 41, Fig. 2, delivers line pressure to a port 77 of the selector 42, to a port 187 of a valve 44 which delivers to a line 186 an output pressure, referred to as throttle pressure, proportional to engine throttle opening, and to a line 64 which, through an orifice 190, is connected to output speed responsive governor valves 59, 60 whereby the pressure in a line 189 is proportional to output speed. This pressure is transmitted to a valve 48 which feeds an amplified speed signal through the outlet 209 of a shuttle valve 58 to chambers at the bases of 3-4, 2-3 and 1-2 shift valves 47, 46, 45, respectively. The throttle pressure in the line 186 has access through a shuttle valve 54 and ports 91, 93 to differential areas 88a, 88b, 88c to provide, together with a spring 89, a downward force on the spool 88 of the valve 45. Throttle pressure is also effective through shuttle valves 55, 57 to provide downward forces on the spools 100, 113 of valves 46, 47. When the selector 42 is in the D position shown, line pressure at the port 77 has access to a port 78 whence it passes through a conduit 180 to the clutch 5. As vehicle speed increases, the spool 88 is raised, closing the port 93 to provide a positive action and hysteresis, and interconnecting ports 94, 95 so that line pressure is delivered through a conduit 194 to the brake 11. Further increase of speed raises the spool 100, closing an inlet 106 from a hysteresis valve 53 and interconnecting ports 109, 110 so that line pressure is delivered through a conduit 200 to a device 34 for applying the brake 12. Furtherincrease of speed raises the spool 113 so that line pressure from the conduit 200 is delivered through a conduit 201 and shuttle valve 56 to the clutch 4 and a device 35 for releasing the brake 12. Due to a connection 195 between the shuttle valve 57 and the hysteresis valve 53 the output from the latter corresponds to throttle pressure or line pressure, depending on the position of the selector 42. The pressure in line 64 is regulated by a valve 43 whose spool is subject on its area 65a to line pressure in the conduit 180 when the selector 42 is positioned for any forward range, and on differential areas 65e, 65f to pressure in a conduit 185 which, due to the shuttle valve 57, is connected to line pressure from a port 79 when the selector is in any of the 1, 2, 3, positions, and to throttle pressure in other circumstances, when the port 79 is isolated from the port 77. An additional pressure acts at 69 on the spool when the engine is idling, this pressure being transmitted through a creep valve 212 from a port 165 of a valve 50. On kickdown or on release of the accelerator a switch 36 is operated to lift a solenoid plunger 203 from a port 204 so that a spool 155 is raised to the position shown to deliver fluid to a port 164 of the valve 50. When the accelerator is released the spool 161 is in its lower position, because of its connection 186 with throttle pressure, so that ports 164, 165 are interconnected and fluid at line pressure enters the shuttle valve 58 from the valve 212 and passes to the shift valves to establish the highest ratio. This action is prevented when the selector is in any of its 1, 2, 3 positions because the conduit 181 is then pressurized from the port 79 so that the creep valve spool 213 is depressed to interrupt the connection 214, 217. On kickdown the spool 161 is in its upper position so that line pressure passes from the port 164 to a port 163 and thence to a chamber above the spool of the valve 48 causing the latter to deliver unamplified governor pressure to the shift valves. Valves 51, 52 deliver reduced line pressure to the brakes 9, 10 when the selector is set at 1 or 2. When reverse is selected line pressure passes from port 77 to port 76 and thence through conduit 191 and valve 51, which does not reduce pressure in this case, to the brake 9. The pressure is also effective through the shuttle valve 56 to engage the clutch 4. All outlets from the selector are isolated from the line pressure port 77 when P or N is selected.