Patent GB-924057-A (GB)
Title: Electrical control system for a change-speed transmission
IPC: F16H61/02
Filed: 1961-05-25
Abstract: 924,057. Change-speed control. EATON MANUFACTURING CO. May 25, 1961 [June 27, 1960], No. 18992/61. Class 80 (2). A device preventing asynchronous engagement of toothed elements in a change-speed gear for motor cars &c. comprises means for providing electrical outputs proportional to the rates of rotation of the toothed elements to be engaged, means for comparing the electrical outputs and effecting shifting of the toothed elements when said outputs reach a predetermined ratio respective to each other, and means for altering the relative values of the outputs before they are compared so that the outputs reach the predetermined ratio slightly before their corresponding toothed elements reach synchronism. Function summary.-Change-speed gearing having input and output shafts 1, 3, Fig. 1, and positive ratio establishing clutches has upshifts and downshifts preselected by manual actuation of valves 133, 134, ratio establishment being later effected by manual actuation of a valve 136, the valves supplying pressure fluid, such as compressed air, to a system comprising a ratio selector 111 stepped in one direction or the other by servo-actuated pawls 118, 119, and upshifts being accompanied by engagement of a countershaft brake 24. During shifts, a servo 46 is energized to restore the gearing to its neutral condition, and a servo 23 is energized to disengage a main clutch 19. Input and output driven generators 216, 217 supply potentials proportional to the speed of the input and output driven shafts 1, 3 to a balance circuit which, when junctions 265, 266, Fig. 3, are out-of-balance, renders a transistor 289 non-conducting so that a switch 307 is conditioned to close a valve 91, preventing establishment of the preselected ratio. An armature 263 is mechanically coupled to the selector 111 so as to tap-off at different points 256 ... 260 along a resistor 248, the ratios of the resistance between a junction point 233 and the respective tapping 256 &c. and between junction points 232, 270 being proportional to the mechanical ratio selected in the change-speed gearing. Condensers 235, 254 in the circuit so act that electrical balance is obtained slightly before mechanical synchronization. When electrical balance has been achieved, the valve 91 is actuated by restoration of the transistor 289 to a conducting condition, and establishment of the ratio is effected, coincident with re-engagement of the main clutch 19. Gearing.-The gearing shown is similar to that of Specification 851,996, and comprises an engine-driven shaft 21, a main clutch 19 which may be disengaged by the car driver on actuation of the usual pedal, an input shaft 1, a countershaft 8 and an output shaft 3, a positive clutch 9 sliding on the output shaft to engage gears 2, 4, and gears 6, 7 sliding on the output shaft to establish engagement with gears fast on the countershaft 8 for establishment of forward ratios and reverse. A fluid pressure engaged disc brake 24 can be actuated to slow the countershaft and the input shaft 1. The ratio selecting clutch and gears are slidden by selector rods 16 ... 18 having at each end servos 1 . . . 5, R energized as described below. Stops 41 ... 43 on the selector rods may be engaged on opposite sides by plates 38, 39 when the neutral servo 46 is energized to squeeze them together, thus disestablishing any ratio engaged in the gearing. Electrical synchronizing control.-When first ratio has been selected, the armature 263, Fig. 3, engages the contact 260, so that the ratio of the resistance between junctions 233, 260 and 233, 250 is the same as the first gear mechanical ratio. Accordingly, the potential supply from the input and output driven generators 216, 217 is in balance. The input generator 216 produces a speed proportional potential at junctions 245, 246 doubled by rectifiers &c. 237, 238. The output generator 217 supplies speed proportional potential through a voltage doubling circuit 220, 221, &c. at junctions 228, 270, the potential at the junction 228 being applied to the junction 233. The potential at junctions 232, 270 is in series with, but of opposite polarity to the potential between the armature 263 and the junction point 233, being applied through a rectifier 271 or a rectifier 277, depending upon its polarity, and thence through junctions 272 or 278 to the transistor 289 and the other of the junctions 278, 272, the junction 265, the armature 263 &c. to the junction 233. In a balanced condition, the potential between the junctions 265, 266 is zero, the transistor 289 conducts, and current flows through a winding 302 of a switch 303. On moving the armature 263 to a second ratio position causing unbalance between the junctions 265, 266, a negative potential is produced at the junction 266. The bias 288 of the transistor 289 is overcome, so that it now becomes non-conducting. Accordingly, the winding 302 of a switch 303 fed through the transistor 289 is de-energized, and closes contacts 319 of the switch. At the same time, the negative potential at the junction 266 causes energization of a coil 282 to actuate a switch 283, de-energizing a relay coil 317 controlling the valve 91. A pressure switch 323 may then be closed by the pneumatic control circuit, as described below, to connect a source of potential P through a relay coil 84 to actuate a valve 76 supplying pressure fluid to the countershaft brake 24. The input generator 216 now decelerates rapidly, but the condenser 254 tends to maintain the previously existing potential, so that the potential between the junctions 259, 233 leads that which it would be without the condenser. Electrical balance across the circuit is thereby re-attained slightly before mechanical synchronization in the change-speed gearing. When balance is again reached, the transistor 289 is restored to its conducting condition and the relay coil 282 of the switch 313 is de-energized to disengage the countershaft brake 24. The original position is then restored, and the preselected ratio may be established. In practice, the speed of the output shaft 3 also slows down during the shift interval. The condenser 235 then tends to maintain the previous potential relationship, and the potential across the junctions 232, 270 diminishes more rapidly than that by normal speed reduction of the output driven generator 217, so that again electrical balance slightly leads mechanical synchronization. During downshifts, unbalance is again caused across the junctions 265, 266, rendering the transistor 289 non-conducting, but the polarity of the current is now such that a rectifier 284 in the circuit of the relay 282 operating the switch 313 prevents the transmission of current therethrough, so that the countershaft brake 24 is not applied. However, the winding 317 of the valve 91 is energized to re-engage the main clutch 19 as soon as neutral is obtained in the gearing. As before, electrical balance is achieved just before mechanical synchronization. Fluid pressure control. Starting.-With the car stationary, a compressed air source S, Fig. 1, supplies pressure to pipes 147, 148, 149 while the main clutch 19 is disengaged on pedal actuation by the driver. The valve 76 is closed, so that the countershaft brake 24 is disengaged. Pressure passes through a relay valve 63 to pipes 151, 127 and through the rotary selector 111 to an appropriate pipe 171 ... 177 leading to the ratio establishing servos 1 ... 5, R. At the same time, pressure in the pipe 148 passes through a valve 93 to pipes 159, 161 and thence to the neutral servo 46, which clamps the plates 38, 39 together and acts on the stops 41 ... 43 on the selector rods 16 ... 18 to hold the gearing in neutral. The neutral servo 46 is larger, and therefore more powerful, than the ratio establishing servos 1 ... 5, R, which it can therefore overcome. If the ratio selector 111 is in its neutral position, pressure is supplied through the pipe 178 to close the valve 93, and prevent energization either of the neutral servo 46 or the clutch servo 23. To select the first ratio, the preselector downshift valve 134 is repeatedly pressed to supply pressure to pipes 140, 143 so that a servo 117 is actuated to engage the pawl 119 with teeth 113 on the selector 111, which is accordingly turned a step at a time to connect a port 126 with the pipe 172. A ratio establishing valve 136 is then depressed to supply compressed air to a valve 97, which first passes compressed air to a pipe 104, built up of backpressure in the latter pipe acting on a piston 102 in the valve 97 to move its piston 102 rightwards, thus closing the entry port of the valve by means of a valve head 101 and venting the pipe 104 to exhaust 106. The pressure pulse supplied to the pipe 104 moves the valve 93 to its right-hand position and connects main pressure 148 to the pipes 158, 161. From the pipe 158, pressure passes through a valve 96 to a pipe 162 and the clutch servo 23, to hold the main clutch 19 disengaged. Pressure in the pipe 161 passes to the neutral servo 46 and restores the gearing to its neutral position. The plates 38, 39 clamped together by the neutral servo 46 act on a crank 51 to move the valve 63 to its left-hand position. Main pressure 148 now passes through the valve 63 to the pipes 151, 127, the selector 111, the pipe 172 and thence to the first ratio establishing servo 1. However, pressure is still maintained in the neutralizing servo 46, so that ratio establishment is prevented. As the car is stationary, the shafts 1, 3 and the input and output driven generators 216, 217 are at rest, and the electrical synchronizing means is inoperative. Therefore the switch 303, Fig. 3, is energized, the valve 92 is tripped and pressure in the pipe 154 passes through a pipe 157 to move the valve 93 leftwards, closing the main pipe 148 and venting the pipes 158, 161, to de-energize the clutch servo 23 for clutch engagement and de-energizing the neutral