Patent GB-782392-A (GB)
Title: Improvements in and relating to a hydraulic control mechanism for a change-speed gear
IPC: F16H61/00
Filed: 1955-07-13
Abstract: 782,392. Change-speed control. COMPAGNIE DE PONT-A-MOUSSON. July 13, 1955 [July 15, 1954], No. 20259/55. Class 80 (2). An output-speed-responsive automatic hydraulic control for a four-speed constant-mesh gear B, driven through a fluid coupling H on a vehicle, has upshift and downshift speeds overlapped to such an extent that downshift speed is equal to that of the next preceding upshift but one, i.e. with 1-2, 2-3 and 3-4 upshifts occurring at vehicle speeds V<SP>1</SP>, V<SP>2</SP>, V<SP>3</SP> respectively, the downshifts 4-3 and 3-1 (3-2 is omitted) occur at speeds V2, V<SP>1</SP> respectively. Also provided is a manual up or down singlestep override which may be controlled by the vehicle accelerator pedal to produce upshift on sudden release and downshift on overtravel kickdown. The four forward speeds (manual reverse, not shown) are introduced by admitting oil pressure, from a single pump 1 driven by the input shaft A, selectively to motors F<SP>1</SP>, F<SP>2</SP>, F<SP>3</SP>, F<SP>4</SP>, respectively, under control of a piston selector-valve S which is actuated in three shiftsteps by three fluid-pressure motors V<SP>1</SP>, V<SP>2</SP>, V<SP>3</SP>, having graduated strokes and acting on the selector-valve S through a spring-loaded platelever 30 and forked slide 26. Shift is initiated by three electro-hydraulic valves in a unit P controlled by an output driven centrifugal governor 78, or, in Figs. 8 and 9, not shown, by three centrifugal valves grouped radially around the output shaft. The downshift overlap and manual override are provided by a valve unit T. Operation. Upshifts. With the engine running and the output shaft C stationary, Fig. 1, the pump pressure-line 5 feeds directly the first speed motor Fl through the selector valve S and line 13a. On accelerating in first speed to a predetermined speed V<SP>1</SP>, the output-driven governor 78 closes a first upshift switch 76a to raise a valve 74a of the unit P, directing line pressure 5, 6 into a line 64 energizing the selector valve motor V<SP>1</SP> which turns the plate lever 30 one step clockwise, shifting the selector valve S one step left to position II. The first speed line 13a now exhausts at 21, 23, 17, 18 and the selector valve S pressurizes the second speed shift motor F<SP>2</SP> through a line 14a, causing 1-2 upshift. At a higher speed V<SP>2</SP>, 2-3 upshift is initiated by governor-closure of contacts 76b to raise a second valve 74b of the unit P, feeding line pressure 5 through the two valves 74a (still lifted) and 74b in series, and a line 65, to move rightwards a spring-loaded hollow piston 49 of the unit T, which forwards the pressure 65 through lines 42, 40, 34 to energize the second selector valve-motor V2. This raises the plate lever 30 one more step up, shifting the selector valve S one more step left, position III, to exhaust the second speed line 14a, and feed a line 15a energizing the third speed shift motor F<SP>3</SP>, completing 2-3 upshift. At a still higher speed V3, the third valve 74c of the unit P is raised by governor-closed contacts 76c, and line pressure 6 flows through the three valves 74a, 74b, 74c in series with a line 66 and thence through lines 44, 35 to energize the selector-valve-motor V3. This steps the selector-valve S to its extreme left, position IV, to energize the fourth speed shift motor F<SP>4</SP> through a line 16a, and exhausts 15a, to produce 3-4 upshift. At the same time the III-IV step of the lever-operated slide 26 causes a spring abutment 63b to move a piston valve 54 of the unit T to the left until ball detents 55 leave the centre of three grooves 53a in the hollow piston 49 (in its rightward position after 2-3 upshift) and occupy the extreme left groove. The selector-valve-motor V<SP>3</SP> remains supplied with pressure, but now from the lines 65, 42, 35, supplied by the second valve 74b of the unit P instead of by the third 74c. Thus, when a return downshift is to be made the second valve 74b causes it at the 2-3 upshift speed V<SP>2</SP>, instead of the third valve 74c at 3-4 upshift speed V<SP>3</SP>. Downshift. On decreasing speed to 3-4 upshift speed V<SP>3</SP>, the governor-closure of the third valve 74c has no effect, but on reaching 2-3 upshift speed V<SP>2</SP>, the governor-closure of the second valve 74b exhausts the line 65, permitting the hollow piston 49 of the unit T to be spring-returned to the left, where it exhausts the selector valve. Motor V<SP>3</SP> through lines 35, 42, 44a, permitting the plate lever 30 and selector valve S to be spring-returned one step down, position III, producing 4-3 downshift. With further decrease in speed to 1-2 upshift speed V<SP>1</SP>, governor closure of the valve 74a exhausts the lines 64, 34 of both selector-valve motors V<SP>1</SP>, V<SP>2</SP>, permitting the selector valve S to make two spring-loaded steps down, posi. tion I, causing 3-1 downshift, and also returning the piston valve 54 of the unit T to its initial position. Manual and kickdown shift. A single step up or down can be made at any time by manually pushing or pulling a spring-centralized knob 61 which operates the piston valve 54 of the unit T through a sheathed cable and fork 59. In Fig. 7, not shown, the fork 59 is actuated through a spring-centralized rod and lost-motion connection by the accelerator pedal, sudden release of which causes upshift, and overtravel depression downshift.