Patent GB-737319-A (GB)
Title: Improvements relating to control means for change-speed gearing
IPC: F16H61/02
Filed: 1952-11-14
Abstract: 737,319. Change-speed control. DAIMLERBENZ AKT.-GES. Nov. 14, 1952 [Nov. 16, 1951], No. 28790/52. Addition to 711,293. Class 80 (2). The hydraulic change-speed gear control of the parent Specification wherein oil pressure supplied to gear-engaging clutches is regulated at D in response to engine-section, and there is a change-over valve U for changing the pressure supply from an input driven oil pump P1 to an output driven pump P2, such change-over valve also effecting a ratio-shift and being displaced in dependence on output speed by the difference in pressures produced by the two pumps P1, P2, which pressure difference is additionally regulated by engine suction, is characterized in that the said suction now acts directly at M on the main pressure-regulator valve D, so that decreased suction causes downshift and vice versa. Automatic shift is between third and fourth ratios only of the four-speed gear. In addition the pressure-regulator D has four control-edges 46, 47, 48, 49 regulating lines 62, 64, 63 and 93 feeding respectively the clutches II, III, IV of second, third and fourth speeds, and a fluid-coupling and lubricating line FC lub, the control edges being staggered so that rightward opening movement of the regulator feeds those lines in the sequence stated, which prevents sudden loss of pressure in the line of a superseded clutch during a shift due to filling the new clutch, so that the shift is rendered more gradual. Torque-overlapped upshift is provided by exhausting a superseded clutch only by pressure build-up in a newly engaging clutch. As in the parent Specification the gear, not shown, is driven through a fluid coupling FC bridged in the highest ratio IV, the top three ratios being introduced by fluid-pressure engaged friction clutches II, III, IV, controlled by fluid-actuated shift-valves SII, SIII, SIV, whilst the first ratio, sharing the pressure-line 62 of fourth, is through a positive dog-clutch I, which remains engaged in higher ratios and is overrun in a free-wheel clutch. Additional to the shift and regulator valves are a manuallyoperated selector-valve W operated jointly with a cross-shift valve GS, a reverse lock valve Rh, a change-over valve U for change-over between input- and output-driven pumps, P1, P2, supplying the system pressure-main 24 (all as in the parent Specification) and a pressurerelief valve V in the line 93, feeding first the fluid-coupling FC, secondly the lubricating line lub and finally exhaust. The shift valves SII, SIV are all moved from right to left to open the pressure supply lines 62, 64 to the respective clutches II, IV by pressure applied to their right faces, the drawing showing third speed in operation, the exhaust of all valves being marked O. Pressure-regulator valve D. Pressure supplied initially to the main 24 through the changeover valve U from the input pump P1 acts through a restrictor 50 rightwards at 41 on the pressure-regulator valve D in opposition to a screw-adjustable spring 55, setting a minimum, and the diaphragm M, loaded by an adjustable spring 60 opposing engine manifold depression acting at 61. The diaphragm acts through a bellcrank 58 turning on an eccentric 57 by which the leverage is adjusted to regulate pressure in accordance with torque at a predetermined excess over torque requirements. The staggered control edges 46 ... 49 regulate pressure in sequence to the feed lines 62-64 and 93 of the clutches and fluid coupling FC, as above referred to. Minimum valve-loading is adjusted so that with closed throttle all these lines are closed and the fluid coupling, not being fed, uncouples the engine from the gearing. Neutral. Initially the selector-valve W is in its second speed position with a notch II<SP>1</SP> underlying a detent 35, and the coupled cross-shift valve GS is in its extreme left position, exhausting the first speed clutch I at O. The second and third speed clutches II, III exhaust through their shift-valves SII, SIII and reverselock valve Rh; the fourth IV through its shiftvalve SIV. Starting in second. The manual lever (not shown), forming a common control for the selector and cross-shift valves W, GS, is operated to move the latter, GS, to its rightward position shown, where it remains for all forward speeds. Pressure fed by the input pump P1 through the change-over valve U to the main 24 branches upwards through the cross-shift valve GS and line 28 to the selector-valve W and thence to the right end 37 of the shift-valve SII shifting it left. The pressure loss caused by opening this line results in the regulatorvalve D moving left, closing all its outlets until restoration of pressure moves it right opening first by control edge 48 the line 63 which through the now-open shift valve SII engages the second-speed clutch II. The subsequent feed by the control edge 46 to the line 62 feeds the first speed positive clutch I through the cross-shift valve, but when the last control edge 49 finally feeds the line 93 of the fluid-coupling FC, the vehicle starts in second, with overrun in first. Pump change-over-is speed- and torqueresponsive. It occurs when the output pump P2, exhausting through the change-over valve port 15 and a restrictor to O, builds up sufficient pressure to act rightwards at 14 on the changeover valve U, overcoming the loading spring 23 and pressure at 22 from a line 25 connected to the end 41 of the pressure-regulator valve D, so that the change-over valve U moves right, exhausting the input pump P1 at 19, 0, and supplying the pressure main 24 from the output pump P2 only, at the same time cutting out the restricted exhaust 15, O, so that return change-over to the input pump P1 can only occur at a lower vehicle speed. The changeover valve U is maintained in its rightward position conditional upon pressure difference between the feed direct to the left end 14 and that to the right end 22 from the line 25, regulator valve chamber 41, restrictor 50 and main 24, from which last-named there is flow through the regulator D to the fluid coupling K. Accelerator depression, by reducing downward load on the diaphragm M, causes a sudden increase of pressure at the regulator valve, in consequence of which the flow provided by the output pump P2 is insufficient to maintain the rightward pressure differential so that the change-over valve U moves back to the left to reintroduce the input pump P1. The pump change-over is thus dependent not only on vehicle speed but also on engine torque as represented by manifold depression at M, increased torque necessitating higher vehicle speed for change-over to the output pump P2. 2-3 Upshift is made by moving the selectorvalve W until notch III underlies the detent 35, position shown, which supplies pressure from the line 28 to the right end 39 of the third speed shift-valve SIII, whilst still maintaining supply to the right end of the second-speed shift valve SII. The third speed valve SIII immediately shifts left, supplying pressure from the regulated line 64 through a restrictor to the third speed clutch III, this clutching pressure also branching to a chamber 82 at the left of the shift-valve SII where, assisted by a spring 85, it eventually overcomes leftward pressure to return the shiftvalve SII to the right, position shown, exhausting the second speed clutch II in proportion as the third-speed clutch III is pressurized, providing a torque-overlapped shift. 3-4 Upshift. Moving the selector-valve W for notch IV to underlie the detent 35 is without effect unless or until the pump change-over valve U has moved right to introduce the output pump P2, whereupon pressure from the line 28 passes through the selector-valve W, and now-communicating grooves 20, 21 of the change-over valve U to the right end 70 of the fourth speed shift valve SIV, which immediately moves left to pressurize the fourth speed clutch IV from the regulated line 62. This clutching pressure also branches to the left end 74 of the third speed shift-valve SIII, where, assisted by a spring 75, it eventually overcomes the pressure still acting leftwards at 39, to shift the valve SIII right for exhausting the third speed clutch III. The same clutching pressure also branches through a port 104 to a space inside a spring- loaded plunger 84 at the left of the second-speed shift valve SII, which plunger is thereby moved right to maintain the shift-valve SII in release position in spite of the exhaust of the space 82 connected to the exhausting third speed clutch III. The final rightward pressure for the plunger 84 is taken through a second port 102 from the still pressurized right end 39 of the third speed shift-valve SIII, which ensures that, on a 4-3 downshift, when the right end 70 of the fourth speed shift-valve SIV and space 82 of the second speed shift-valve SII are both exhausted, pressure is still available for maintaining the second-speed shift-valve SII in its rightward release position. The 3-4 upshift is thus also torque overlapped, and both upshift and downshift occur automatically under control of the pump change-over valve U, providing the manual selector-valve W has been set in fourth-speed position. First speed is by moving the selector-valve W for notch I<SP>1</SP> to underlie the detent 35, which exhausts the right end 37 of the second speed shift valve SII, thus disengaging the second speed clutch II and permitting the already engaged first speed clutch I to pick up the drive through its free wheel. If the shift to first is made directly from neutral, the first speed clutch I will not be already engaged, and in this case second speed must be passed through and remain engaged for a short time to synchronize the positive first speed clutch I. Other details are as in the parent Specification.