Patent GB-1331352-A (GB)
Title: Vehicles having fluid power control systems
IPC: B60T11/10
Filed: 1971-08-11
Abstract: 1331352 Change-speed control TWIN DISC Inc 11 Aug 1971 [24 Aug 1970] 37602/71 Heading F2D In a manually controlled fluid-pressure operated forward-reverse and multi-ratio transmission on a motor vehicle, such as a front-end loader, a speed-responsive inhibitor valve 50, activated by an output-driven positive displacement pump P, Fig. 2, prevents establishment of a selected change of direction above a predetermined vehicle speed, or downshift above a second predetermined speed, but instead causes application of the vehicle service brakes, also by fluid pressure, the degree of such pressure being under the manual control of the forward or reverse shift-valve, which, in turn, causes release of a main clutch 2, until the speed falls below the predetermined values, whereupon the commanded direction change or ratio shift is established. Gear arrangement.-The gear, (Fig. 7, not shown), includes a modulatable main clutch (2), an hydrodynamic torque converter, a parallel shaft gear drive with a forward clutch 6 and reverse clutch 7, and first and second ratio clutches 8, 9, all the clutches being frictional and fluid-pressure engaged. A power take-off is from the reverse gear. Fluid pressure supply and regulation.-A single input-driven pump 15, Fig. 3, supplies the system through a filter, heat exchanger and main regulator 20, set to provide a "high hold" pressure of 205 p.s.i., thus pressure 26, being the final pressure applied to the transmission clutches on shift completion. Three additional regulators 21, 22, 23 with proportionately lower loadings supply respectively a clutch apply pressure line 25 at 160 p.s.i., for shift initiation, a torque-converter feed line 27a at 60 p.s.i.; and a lube line 28 at 22 p.s.i.. Line 27 feeds the modulatable main clutch. Manual controls.-Forward and reverse clutches 6, 7 and service brakes are controlled respectively by valves 35, 36, 37, Fig. 1, which are operated through springs against a feedback load to provide feel and graduated pressure control. The forward-reverse valves 35, 36 are operated by rocking forward-reverse pedals 38, 39, Fig. 6, selectively by the right foot whilst the brake-valve 37 is operated by a single left-foot pedal 40, which applies the service brakes and also releases the main clutch in all settings except power take-off. A selector valve 42, Fig. 1, selects power take-off, neutral, first and second ratios and is operated by a gate-guided lever 43, Fig. 6. Circuit valves.-In the supply lines 63 ... 66 of the forward-reverse and ratio clutches 6...9 are "cross-over" valves 51 ... 54, which are loaded in opposite directions by pistons 55, 55a &c. pressurized by corresponding clutch-lines to form a fluid interlock between 6 and 7, and 8 and 9, so that, during a shift, or direction change, increase in pressure in an incoming clutch shifts the cross-over valve of the outgoing clutch to exhaust the latter at an appropriate stage to provide an overlap shift. Valves 83, 86 and 154, 156 are relay valves through which the respective clutch lines are supplied or exhausted. Valve 152 is a pressure-reducing valve which supplies a low pressure to both forward and reverse clutches 6, 7 in neutral, to maintain light slipping engagement avoiding creep and reducing slip on subsequent drive engagement. At this time a light spring engages the main clutch. Feed-back relay valves 170, 180 supply the service brake and main clutch graduated engaging pressures. Application of the service brake always disengages the main clutch 2, apart from power take-off operation. A lubrication safety valve 150 exhausts the main clutch when lube pressure 28 is low, and also allows the operator to engage the main clutch during power take-off operation, whether or not the service brakes are applied. Inhibitor valve 50 has similar reverse and downshift inhibitor valves, 80, 110, Fig. 2. In the former, pressure in either end chamber 124, 125, in accordance with the direction of flow and speed of an output-driven pump P, shifts the valve-spool 120 to one end or the other, blocking communication between the forward or reverse valve 35 or 36, and its clutch control line 84, 85 or 81, 82, and substituting a communication from the blocked line 84 or 81 a line 41, and check valve 41a, to the brake control valve 170. Thus if either the manual forward or reverse valve 35 or 36 is operated to change direction above a predetermined speed, reversal is inhibited, service brake application substituted therefor, and the main clutch disengaged, the service brake pressure being manually controlled by the forward or reverse shift-valve 35, 36, until speed falls below the set value, whereupon the valve 120 centralizes and direction change ensues. The downshift inhibitor valve 110 acts similarly at a higher speed, but in its case supplies pressure to a line 139 which depresses the first speed relay valve 154, preventing downshift. Restrictors 87 &c., connected to high hold pressure 26, and one-way valves 133, 134, act to control the set speeds and act to ensure substantially no pressure change across the pump P. Complete circuit and function.-Fig. 1 shows the parts with power take-off selected at the selector valve 42, the forward, reverse and stop valves 35, 36 being unoperated. High hold pressure 26 is blocked at the cross-over valves 51 ... 54, which, in the absence of pressure bias in either direction, are maintained in a rightward neutralizing position by springs. Apply pressure 25 reaches all the clutch relay valves 83, 86, 154, 156 but these are unoperated so that all the clutches 6, 7, 8, 9 are exhausted, the main clutch 2 also being exhausted at its control valve 180. The power take-off is to be driven through the main clutch 2, torque-converter and forward or reverse clutch 6 or 7 (not the vehicle drive ratio clutches 8, 9). To cause modulated engagement of the power take-off in forward or reverse, the forward or reverse valve 35 or 37 is loaded by its pedal to take in high hold pressure 26 from the selector valve 42 and line 41b and supply modulated pressure 84 or 81 through the inhibitor valve 50 and line 85 or 82 to actuate the forward or reverse relay valve 86 or 83, engaging the clutch 6 or 7 and loading the cross-over valve 52 or 51 right to ensure exhaust of 7 or 6. Selector valve 42 also passes high hold pressure 49 to maintain the first and second ratio cross-over valves 53, 54 in exhaust position. Pressure also passes through the selector valve 42 to shift leftwards a valve 158, breaking a pressure line to the safety lubrication valve 150 so that the main clutch 2 can be engaged with the service brake applied. Modulated pressure 84, 151 now passes through the valve 150 to produce modulated operation of the main clutch valve 180, providing modulated power take-off drive in either direction. Neutral setting of the selector valve 42 pressurizes lines 48, 49 holding all the cross-over valves 51 ... 54 in their rightward position. This exhausts the first and second ratio clutches 8, 9 through their relay valves 154, 156, but, for the exhaust path from the relay valves 86, 83 of the forward and reverse clutches 6, 7, there is substituted a low pressure supply derived from the pressure-reducing valve 152, which, in the normal position shown, provides an exhaust path for the relay valves, but which, in neutral, is loaded upwards by high hold pressure from the selector valve 42, to substitute the low pressure supply, which passes through the relay valves 86, 83 to cause light slipping engagement of both forward and reverse clutches 6, 7, which avoids creep and reduces slip during subsequent full engagement. The main clutch is engaged by a light spring. First speed setting of the selector valve 42 supplies high hold pressure at 162 to raise the first speed relay valve 154 engaging the first clutch 8, pressure 162 also passing to the forward-reverse valves 35, 36 through a line 41b. Graduated depression of the forward or reverse pedal then loads the appropriate valve 35 or 36 to direct modulated pressure to a line 84 or 81 and thence through the inhibitor valve 50 (if permitting) to operate the relay valve 86 or 83, which then supplies apply pressure 25 to the clutch 6 or 7, which pressure shifts its cross-over valve 51 or 52 left to substitute finally high hold pressure 26. The modulated pressure 84 or 81 from the forward or reverse valve 35 or 36 also passes through the lubrication safety valve 150 to load the main clutch valve 180 leftwards and produce modulated clutch engagement. For the 1-2 upshift, the selector valve 42 in its second ratio position exhausts the first speed line 162 and pressurizes the second 166, releasing the first relay 154 and depressing the second relay 156, which latter pressurizes the second clutch 9 with apply pressure 25. With its crossover valve 53 still in the leftward position, the first clutch 8 remains fully engaged until pressure build up in the second clutch 9 passes through a line 65 to shift the cross-over valve 53 right, thereby effecting a timed release of the first clutch 8. Finally pressure in the clutch 9 shifts its cross-over valve 54 left substituting high hold pressure 26 for apply pressure 25 in the clutch 9. Other shifts, including forward-reverse are similar, and the inhibitor valve 50 provides speed-responsive restriction as above described.