Patent GB-1161341-A (GB)
Title: Governor Device for Effecting Control as a Function of Rotary Speed and of at least one Auxiliary Parameter
IPC: G05B11/14
Filed: 1966-08-24
Abstract: 1,161,341. Controlling change-speed gearing. REGIE NATIONALE DES USINES RENAULT. 24 Aug., 1966 [10 Sept., 1965], No. 38080/66. Heading F2D. [Also in Division H3] A control device, e.g. for an automatic gearbox on a motor vehicle, compares a signal emanating from a tachometric pick-up connected to a shaft, e.g. the gear-box input or output shaft, with the striking time of a unijunction transistor the duration of the tachometric signal being variable also by an auxiliary parameter, e.g. the opening of the engine throttle, and the transistor circuit supplying control signals by means of an output circuit to effect gear change; the output circuit additionaly controls the striking time of the unijunction transistor, by means of a voltage divider 26, 36, 39 in order to obtain a differential between upshift and downshift speeds of the shaft. The input or output shaft 1 of the gear-box is provided with a plate 2, either side of which are light waveguides 3, 4 supported by a pin 7 pivoting in support 8 under the action of accelerator pedal 9. Thus, the duration of the light signal received by a photo-resistive cell 6 from a source 5, depends on the speed of rotation of shaft 1 and the setting of pedal 9. The cell 6 is connected at A to the base 13 of a transistor 14, e.g. of the NPN type, through capacitor 12, and is supplied with D.C. from a source 16. The transistor 14 is provided with a resistor 21 inserted between its emitter and the negative terminal 18 of source 16, and at point E of its collector with a variable resistor 22 and a capacitor 23. The point E also forms part of the emitter of a unijunction transistor 24 having bases B1, B2 connected to the current source 16 through resistors 25, 26. The base B1 is additionally coupled to transistor 29 which, together with a transistor 30, forms a bi-stable flip-flop, the collectors of which transistors are connected to the current source through a resistor 32, and a coil 31 controlling a member, e.g. an electromagnetic valve, which monitors gear changes. Operation shaft 1 not rotating.-A capacitor 12 prevents the potential at A from influencing the base 13 of transistor 14 which remains non- conductive whether cell 6 is illuminated or not. Unijunction transistor 24 is struck, the value of resistor 22 being such as to provide a current above that of the valley current of transistor 24. The voltage set up across resistor 25 is transmitted to the base of transistor 29 through a diode 28, rendering this transistor conductive, energizing the coil 31, producing engagement of first gear. Shaft 1 rotates.-The cell 6 is illuminated and darkened twice per revolution, the potential at A being alternately positive and negative, and of square-waveform, this wave being transmitted to the base 13 of transistor 14, which becomes conductive when the cell 6 is in darkness, the potential at A then being positive, and deenergizes the unijunction transistor 24 by taking up the current supplied by resistor 22. When the cell 6 is then illuminated, the transistor 14 becomes non-conductive, charging capacitor 23 by way of resistor 22. If the speed of shaft 1 is below the upshift speed, the unijunction transistor 24 is struck, the resultant voltage set up across resistor 25 being transmitted to the base of transistor 29 to confirm the conduction of this transistor. If the speed of shaft 1 exceeds the upshift speed, the transistor 14 is rendered conductive by darkening of the cell 6 before the capacitor 23 has been discharged through unijunction transistor 24. A large voltage pulse is set up across resistor 21, which pulse is transmitted through normally closed contact 41, and diode 40, to the base of transistor 30 rendering the latter conductive, and de-energizing the coil 31, to upshift the transmission. Up-shift/downshift shaft speed differential.- This differential is obtained by a voltage divider consisting of resistors 26, 36, a diode 37, and the transistor 29, which voltage divider lowers the voltage of base B2 of unijunction transistor 24 when the coil 31 is energized, at a low speed of the shaft 1. The striking of the unijunction transistor is consequently effected after a shorter interval of time corresponding to a higher desired speed of the shaft 1 than when the speed of this shaft is lowered. In the latter case, the voltage at base B2 is substantially equal to that of the terminal 17, the transistor 30 not being energized. This differential may be reduced by means of a contact 38 which is closed when the accelerator pedal 9 is fully depressed, and is effectively substituted for transistor 29, rendering it possible to effect downshift very near to the upshift speed of the shaft 1. Engine braking.-Engine braking is provided by opening a normally closed contact 41 which holds the gear in a low ratio and prevents upshifts therefrom. Closing the contact maintains the transistor 29 conductive or, when the speed falls below a safe value, allows the transistor 29 to become conductive and prevents the transistor 30 from becoming conductive with increasing speed. In an alternative embodiment, Fig. 5 (not shown), a solid-state thyratron (42), e.g. a silicon thyratron, is provided between the part E and the negative terminal 18 of the source 16, in series with a resistor (43) which limits the strength of the change-over current. The control electrode of the thyratron is connected to base B of the unijunction transistor (24) through a resistor (44). A current pulse at base B1 renders the thyratron conductive until the transistor 14 cuts off its anode voltage. In an alternative tachometric pick-up, Fig. 6, (not shown), of the magnetic type, the diamondshaped plate 2 is of ferromagnetic material, and extends between the frusto-conical ends of polepieces (3), (4) provided on a magnet (45) connected to the pin (7). The flux variation due to rotation of the shaft, induces in a coil (46) a current which acts on the base (13) of transistor (14), a diode (47) between the coil and base preventing the application of inverse voltages to the base. In a further alternative the flip-flop comprising transistors 29, 30 are replaced by a solid-state thyratron having on/off control, one of the control signals being optionally derived from a C-R network, and the corresponding diode (28), (40), inverted to apply to the thyratron signals conforming to its nature, by methods known per se. A number of speed ratios may be controlled by a common cell 6 by disposing a corresponding number of electronic detectors in parallel at A. No devices to compensate for temperature variation of the transistors, or for regulating voltage variation of the source are required since, these variations do not modify the intrinsic ratios of the unijunction transistor, nor consequently its striking time.