Patent GB-1252683-A (GB)
IPC: B60K23/02
Filed: 1969-02-17
Abstract: 1,252,683. Change-speed control. ROBERT BOSCH G.m.b.H. 17 Feb., 1969 [16 Feb., 1968], No. 8548/69. Heading F2D. To restrict to a minimum the loss of vehicle speed during a synchronized manual upshift in a heavy vehicle transmission, four signal devices 23 ... 26, which control respectively declutching, input braking, neutralizing and gear establishment, are subject to precise timing control in a co-ordinated cycle. A fifth signal 27 may be provided to maintain engine fuel feed at idle during the shift. Synchronization is provided, not by direct speed comparison, but by predetermined control of the duration of input braking interval. Where the ratio steps are equal this braking interval is fixed, but where they differ, the interval is preselected for the appropriate step by the manual selector. Mechanical selection detail.-Two three-position gear strikers are both moved to central neutral positions by supplying pressure air or liquid through a neutralizing valve V 1  to two opposed pairs of cylinders 8 ... 11, and in either direction to selected gear positions by venting singly an appropriate cylinder by electromagnetic valves Va ... Vd (see Fig. 2, not shown). Equal ratio-step system. Fig. 1.-Energization of the four shift valves Va ... Vd is under control of a manual shift lever and, for upshift only, of the signals 23 ... 27. Untimed downshift.-After preselecting the required downshift by the manual lever 13, the driver presses a button 14 to change over switches 15, 17, which disconnect the shiftvalves Va ... Vd and neutralizing valve V 1  respectively from the signals 23 ... 27 and connect them to driver-operated switches 16, 19. The driver then depresses the clutch pedal at K and closes the switch 19 (which actions may be co-incidental), energizing the neutralizing valve V 1  and neutralizing the gear. On finally closing the switch 16 by the driver, the preselected shift valve Va ... Vd is energized, completing the downshift. Timed upshift.-After preselecting the desired upshift at the lever 13, the driver presses a button 21 to trigger the signals 23 ... 27 (described below) by pulsing a line 22 through a sixth signal 20. Subsequent action of the signals, with suffixes a, is represented on common time scales t in Fig. 3. Upon receiving the short pulse 20a from signal 20, the signal 23 disengages the main clutch 3 at K with a pulse 23a of duration t 1  only sufficient to permit unloading of the transmission so that it can be neutralized by a longer pulse 25a from the signal 25, which pulse is a hold on with sufficient duration to cover the longest synchronizing interval. Signal 24 engages the input brake 32 with a pulse 24a of duration t 2 , precisely timed to synchronize the constant step-up ratio of the gear. The signal 27 maintains engine fuel supply at idle with a long pulse 27a. After a timed delay s, covering the longest synchronization period, the signal 26 provides a pulse 26a for a period t 3 , to energize the preselected shift valve Va ... Vd, which engages the new ratio synchronously and with the clutch fully engaged. With engine fuel-feed restored, shift is completed and the free engine timed is held at a minimum value. Unequal ratio-step system.-Where the three ratio-steps of the four-speed transmission are all different, three separate signals (24<SP>1</SP> ... 24<SP>111</SP> and 26<SP>1</SP> ... 26<SP>111</SP>), Fig. 8, not shown, each timed for the particular step, are used respectively for the synchronizing brake and shift-valve control, and are switched in, as appropriate, by mechanical connection with the selector lever 13. Alternatively, Fig. 9, not shown, single signals may be used, as in Fig. 1, with their timing adjusted by the selector lever 13. Signals.-These, 20 ... 27, may be monostable multivibrators (not further described) or as in Figs. 4 to 7, not shown, circuits using valve diodes for charging adjustable resistancecapacity circuits energizing hold-on relays. The shift-valve signal 26, providing delay-time s, Fig. 3, has two diodes and two holding relays (Fig. 5, not shown) or a single diode and relay with change-over switches 50 ... 53 operated by the gear strikers (Fig. 6, not shown). Modification.-Fig. 9, not shown, provides a change-over switch (V) for controlling a downshift circuit in which synchronism is produced by speed comparison by means not described.