| 摘要 |
<p>933,642. Fluid pressure servomotor control systems. DOWTY HYDRAULIC UNITS Ltd. Jan. 29, 1960 [Jan. 30, 1959], No. 3413/59. Addition to 878,511. Classes 69 (2) and 135. The invention described and claimed in the parent Specification is modified in that the manually operable setting means controls both pump displacement and prime mover speed. A diesel engine 1 drives a variable positive displacement pump 2 connected by pipes 3 and 4 to a positive displacement motor 5 the output shaft 6 of which is connected to the vehicle wheels. The pump displacement is adjustable by a servomotor 25 under the control of a hand lever 68 acting through a shaft 69, cam 74, link 28, spring unit 27 and the rod 26. The pipes 3 and 4 which receive make-up fluid under pressure from an auxiliary pump 18 are connected by conduits 29, 31, respectively, to plungers 35, 36 which are loaded by a spring 38 the compression of which is variable by a cam 41 on the rod 26. The compression of the spring 38 is at its maximum when the pump is at zero displacement, i.e. when the hand-operated lever 68 is in its central position. If, at any given pump displacement, the pressure in either of the pipes 3, 4 should exceed that determined by the cam 41 and spring 38, the corresponding plunger 35, 36 is moved to allow fluid pressure to act on a piston 62 which is moved against a spring 63 to connect the pressure fluid to one or other of the pistons 47, 48 which moves the cam 41 and the rod 26 in a direction to reduce the pump displacement. This arrangement prevents stalling of the diesel engine by excessive movement of the lever 68 or if the vehicle is climbing a steep incline. The speed of the diesel is selected by positioning the control-bar 8 of the fuel injection pump 7 through a cam 73 on the shaft 69, the rod 14, the piston 11, the spring 12 and the diaphragm 9. The selected speed is maintained by subjecting the diaphragm to the pressure at the throat of a Venturi 16 in the air inlet manifold. The profiles of the cams 73, 74 are such that the diesel speed adjustment is effected evenly throughout the complete movement of the lever 68 whereas the pump displacement adjustment is only effected during the first 15 degrees of movement of the lever 68 from its central position. Specification 933,643 also is referred to.</p> |
