Patent GB-1318898-A (GB)
Title: Control system for an automotive automatic power transmission
IPC: F16H47/08
Filed: 1970-10-14
Abstract: 1318898 Change-speed control NISSAN MOTOR CO Ltd 14 Oct 1970 [18 Oct 1969 4 Nov 1969] 48894/70 Heading F2D An electronic control, for 1-2 and 2-3 solenoid shift-valves 59, 61, operating ratio-selecting clutches and brakes in an automatic transmission on a motor-vehicle, responds to output speed and engine-throttle for normal shift, and also to gradient, service-brake application and engine temperature to raise the shift-speeds, and in addition there is an output-speed varied neutral dwell on downshift, during which the engine throttle is operated to synchronize the shift by a signal from a unit 72, comparing output and engine speeds. In the event of electrical failure, first and third ratios are obtained without further action in I and D settings of a manual ranging valve 55. Gear arrangement.-The gear, shown diagrammatically in Fig. 1 only, is a two sun-ring train Simpson gearset, with two selective input clutches, a gear 16, engaged for all forward ratios, a front 15, engaged for direct-drive high and reverse. Reaction for second ratio is taken by a brake 17; for one-way low by a one-way brake 21; and for two-way manual low and reverse by a brake 18. The clutches and brakes are all fluid-pressure operated. The gear is driven through a torque-converter 13, or centrifugal or electromagnetic clutch. Fluid pressure supply and regulation.-A single input-driven pump 45 supplies line pressure 111 under control of a pressure-regulator valve 47 loaded positively by a spring and by TV pressure 133, responsive to engine intake depression 143, provided by a TV valve 50. Negative loading (downward) for line-pressure cut-back is provided by cut-back pressure 149 derived from TV 133 through a restrictor 144, supplying a chamber 148 having an exhaust nozzle 147, variably throttled to produce a variable back pressure by a plunger 146 controlled by a solenoid 145, energized so that line pressure is cut back above a predetermined speed by the electronic circuit detailed below. Pressure is augmented in R and P settings by a line 132. Fluid control system includes a manual PRND21 valve 55, and 1-2 and 2-3 shiftvalves 59, 61, moved rightwards for downshift in opposition to upshift spring bias by energizing solenoids 59a, 61a. In all forward settings of the manual valve 55 the forward clutch 16 is directly engaged. In setting D, initially both solenoid valves 59, 61 are energized, so that only the forward clutch 16 is engaged and drive is in one-way low. Pressure is fed to the 1-2 shift-valve 59 through a line 162. When the electronic circuit de-energizes the 1-2 valve solenoid 59, the brake 17 is applied for second ratio, whilst for third, the 2-3 valve solenoid 61 is additionally de-energized to release the brake 17 and engage the direct-reverse clutch 15. In manual 2 setting the selector valve 55 supplies the same shift-valve line 162 as in D, but now a linked selector switch 89, Fig. 1, deenergizes the 1-2 valve 59 for second ratio. In manual 1 the same shift-valve line 162 is again supplied, but now the switch 89 deenergizes the 2-3 valve 61, whilst keeping the 1-2 valve 59 energized, which causes engagement of the low-reverse brake 18 through the 2-3 valve. If 1 is entered at high speed, a shift to second precedes automatic establishment of low. Also provided is an emergency low valve 65, which is moved leftwards against spring pressure by pressure fed to a line 163 in 2 and 1 settings of the manual selector valve 55, to block the supply of pressure 197 from the 2-3 valve 61 to the direct-reverse clutch 15, so that in both these settings, engagement of that clutch 15 cannot occur even in the event of electrical failure, which would permit upshift of the shift-values 59, 61. In that event setting 1 selects one-way low whilst settings D and 2 both give third ratio. In R setting the manual valve 55 supplies the 1-2 shift-valve 59 through a different line 161, which, through both de-energized shift valves 59, 61 engages the low-reverse brake 18. Pressure is cut off from the line 163, as in D setting, which permits the emergency low valve 65 to open and supply engaging pressure to the direct-reverse clutch 15. In both N and P settings the direct-reverse clutch 15 is engaged to reduce shock on entering reverse, and line pressure is augmented in both P and R by pressurizing the line 132, which provides for a quick engagement of reverse from park. Electrical circuit, Fig. 1.-The boxes shown are not described. Position and speed responsive signals 78, 86 from an accelerator-operated potentiometer 77 and output-driven generator 85, are fed to a shift-pattern generator 70 which issues signals to a solenoid control unit 71 selectively energizing the shift-valve solenoids 59a, 61a. Also signalling the shift-pattern generator are a service brake switch 81, an inclinometer 81 and an engine temperature switch 83, which increases the shift speeds on brake application, on up or down grade running and at low engine temperature respectively. Synchronizing. During downshift the transmission is held in neutral for a period, which is increased with increase in vehicle speed, by a downshift timer 75, controlled by a vehicle speed discriminator circuit 73 receiving the output speed signal 86. During this neutral interval the transmission input and output speeds are synchronized to the new ratio by actuating the engine throttle 97 by a signal 98 from a speed comparator unit 72, receiving the output speed signal 86, an engine speed signal 96 and a signal from the shift pattern generator 70. On attainment of synchronism the comparator unit 72 issues a signal 91 to the valve solenoid control unit 71 allowing the shift to complete. Engine safety.-The vehicle speed discriminating circuit 73 and the shift pattern generator 70 also signal an engine protector circuit 74, a signal from which prevents the solenoid valve control circuit 71 from downshifting if excessive engine speed would result. Line pressure cut-back.-The vehicle speed discriminating circuit 73 also controls a line pressure circuit 76 which controls the energization of the solenoid 145 (Fig. 4) of the cutback valve 53, which reduces the main regulator valve loading at higher speeds.