GB933950A - Improvements in or relating to variable ratio power transmission apparatus - Google Patents

Abstract

933,950. Change speed control. HOBBS TRANSMISSION Ltd. March 8, 1962 [March 21, 1961], No. 10265/61. Class 80 (2). In a change speed control for a motor vehicle, such as in Specification 738,590, output speedresponsive ratio-determining fluid pressure acting on a shift valve, such as that 12 in Fig. 3 of Specification 738,588 is exhausted through two or more axially spaced exhaust ports therein under the control of a valve 29, the piston 24 of which is both axially and rotatably movable and is connected to the accelerator pedal so as to effect an increase in upshift speeds with normal throttle opening and, for kickdown shift, a further increase when the pedal is depressed beyond the full throttle position. The valve 29 comprises two or more channels, such as 41, connected to the shift valve exhaust ports via a selector valve such as 55 in Fig. 3 of Specification 738,588. The piston 24 has an exhaust outlet bore 5 in communication with pairs of exhaust openings such as 32, 33 respectively small and large which, via grooves 36, 37, are alternatively brought into communication with the channels 41 by axial piston movement. The grooves 36 may be concentric but extending only. part way around the piston, or, as shown in Fig. 2, eccentric so as to vary the effective size of the exhaust openings 32 with piston rotation. A lever 12 rocked by the accelerator pedal 10 is connected to the usual butterfly throttle valve 16 by a wire 13 and to a spindle 20 by a rod 18 and an arm 19. The spindle 20 actuates the valve 29 and loads a relief valve 22 which corresponds to the valve 53 in Fig. 3 of Specification 738,588 and which is arranged to increase change speed gear clutch and brake engaging pressure over the initial part of the throttle opening. An arm 46 on the spindle 20 acts on a beam 44 engaging a spring 45 and directly, or by ball joints, a spring abutment pin 25 of the valve 22 and a pin 27 of the piston 24, so that during the first part of the accelerator pedal travel the relief valve 22 abutment is moved to increase engaging pressure until the beam contacts a stop 26 on the valve 22, and during further pedal travel the piston 24 is axially moved. During accelerator pedal travel the piston 24 is rotated by a further arm 48 on the spindle 20 acting, through a rod 47, on an arm 49 of the pin 27. In operation, with the throttle closed the channels 41 will be in line with the shallow portions of the groove 36 as shown in Fig. 2 for reduced effectiveness of the small openings 32 causing shift at lower speeds. As the piston 24 is rotated during normal throttle opening the channels 41 will become increasingly into line with the small openings 32 causing increasing shift speeds. In the kickdown position the large openings 33 are in line with the channels 41 for shifts at still greater speeds. Smooth up and down shifts are obtained since shifts are possible at very low speeds with the throttle nearly closed. At such low speeds the centrifugal valve of Specification 628,499 will cause at least part main clutch disengagement, so that on throttle opening the engine can accelerate sufficiently before complete clutch engagement to ensure smooth ratio shift. Specification 808,318 also is referred to.