Patent GB-1141919-A (GB)
Title: Improvements relating to arrangements for automatically shifting a change-speed gearing for vehicles
IPC: F16H61/06
Filed: 1966-12-02
Abstract: 1,141,919. Change speed control. DAIMLERBENZ A.G. 2 Dec., 1966 [4 Dec., 1965], No. 54146/66. Heading F2D. In an automatic hydraulic control of a change speed gear, such as a planetary gear in a motor vehicle, wherein individual gears are established by brakes or clutches actuated by hydraulic servomotors via shift valves, a plurality of said servomotors are connected to a single common accumulator 10 influencing pressure build-up in the servomotors, and a leakage loss replacing and accumulator speed regulating valve 35 responsive to discharge pressure of said accumulator is arranged in a direct supply line to the shift valves. The four forward speed gear control valve arrangement shown (in part) controls brakes B 1  (B 2 ) and clutches K 1 , K 2 , not shown, First gear being established by engagement of brake (B 2 ), Second gear by brakes (B 2 ) and B 1 , Third gear by brake (B 2 ) and clutch K 1 , and Fourth gear by clutches K 1  and K 2 . The accumulator 10 is effective for engagement of Second, Third and Fourth gears only. The control includes a 1-2 shift valve 23 leading to the brake B 1 , the brake B 1  being disconnected in 3rd gear by shift (not further described) of a valve 25; and 2-3 and 3-4 shift valves 27, 29 respectively leading to the clutches K 1 , K 2 . Engagement and disengagement of the brake (B 2 ) is not described. The accumulator 10 comprises a piston 12 separating supply and accumulating spaces 18, 19 and acted on by springs 13. One or two of the inner of the springs 13 act on a plate 16 carried by a push-rod passing through the piston head 14, so that in the bottom position of the piston only the outer springs are operative, thus providing a weaker spring force at said bottom position. The accumulating space 19 is connected to a line 20 in turn connected to lines 24, 26, 28 connected respectively to the shift valves 23, 27, 29. To permit engine braking in 1st, the clutch K 2  may be engaged via a line marked (K 2 ). Regulated pressure fluid is fed to the supply space 18 through a line 17. A line 21 connects the line 17 to the shift valve 23 via a throttle 22 and connects with the lines 24, 20 in the upshifted position of the valve 23. The piston 36 of the regulating valve 35 is acted on at its top and bottom ends by pressures in lines 37, 38 so connected respectively to the line 20 and to the line 21 (and hence, via the valve 23, the line 24) that the piston 26 is responsive to pressure difference across a measuring throttle 39 in the line 20. A chamber 41 in the regulating valve is connected to the lines 17, 21 by lines 40, 42 respectively. Operation.-As shown, the control is in 1st gear position. For 1-2 shift, the valve 23 is shifted and flow from the line 17 to the brake B 1  and also, via the line 20, to the space 19 is directed through the space 18 and lines 31, 21. When flow in the line 24 ceases, when the brake B 1  is pushed into engagement, the pressure downstream of the throttle 22 increases and the piston 12 is moved downwardly. After closing- off the line 31, further inflow is through the throttle 22 only, for gradual actuation of the piston 12 and gentle gripping of the brake B 1 . For 2-3 shift, with the accumulator in its bottom position, the valve 27 is shifted to connect the line 26 to the clutch K 1 . During clutch servo piston movement the pressure in lines 26, 20 drops and the full pressure in the space 18 begins to move the piston upwardly, residual clutch K 1  servomotor filling taking place through the uncovered line 31. As soon as the clutch K 1  servomotor is filled, rising pressure in the lines 26, 20 moves the piston 12 down again and the remainder of the operation is as described for 1-2 shift, 3-4 shift accumulator operation is that of 2-3 shift. If no pressure difference exists across the measuring throttle 39, the lines 40, 42 are connected for leakage loss replacement without pressure drop. On downward accumulator piston movement, pressure in the line 21 exceeds that in the line 20 below the throttle 39, consequently the regulating valve piston moves upwards and, by throttling the line 40, the flow through the throttle 39 and the accumulator piston speed is regulated. On upward accumulator piston movement, the regulating valve piston moves downwards, causing, firstly, the line 40 to be closed and, secondly, after further movement, connection of the lines 37, 42 and connection of the accumulator to the clutch servomotor, by-passing the measuring throttle 39. To prevent excessive inflow to the regulating valve, a throttle, larger than the throttle 22, may be inserted in the line 40.