Patent GB-496754-A (GB)
Title: Improvements relating to devices for control and operation by fluid servo-motor
IPC: B60K17/08
Filed: 1937-04-30
Abstract: 496,754. Fluid-pressure servomotor systems ; gearing ; brakes. FLEISCHEL, G. April 30, 1937, No. 12351. Convention date, May 7, 1936. [Class 135] [Also in Groups XXIV and XXXIV] In fluid-pressure servomotor controls for clutches on motor vehicles, the valve-member 47, Fig. 2, supplying the clutch servomotor control is primarily operated by a force dependent upon engine speed but is subjected to an auxiliary force due to fluid pressure in such manner that the rate of engagement of the clutch gradually diminishes. The apparatus is shown employed in a vehicle in which the main clutch B, Fig. 1, following the engine A, is operated by levers 9 controlled by a pedaloperated shaft 12 or by a servomotor 14, 17 served by a valve G comprising the valvemember 47, the fluid pressure disengaging the clutch against spring pressure. Oil or other liquid or gas under pressure or suction may be used as the operating medium. A manuallycontrolled reversing-gear C driven by the clutch precedes two epicyclic or other, for example, electromagnetically controlled, speed gears D, E in series controlled by valves D<1>, E<1> which are controlled, Fig. 1, by the driver. The valve G automatically controls the clutch during starting and stopping of the vehicle so that clutch engagement normally commences at a predetermined speed and is complete at a higher predetermined speed, and a further valve H is combined with the valve G to produce the necessary clutch operations during gear changes, during which no movement of the valve-member 47 need occur. An enginedriven centrifugal governor 41 is linked to the valve-member 47 to displace it to the right, Fig. 2, on speed increase to control ports 48, 49 respectively fed from a pump 1, provided with a pressure-limiting valve in the system, and discharging through the valve H to exhaust. A free port 50 supplies the clutch servomotor through a pipe 15. The land 47b of the valvemember 47 is larger than the land 47a so that oil in the space between the lands exerts an auxiliary force on the member which falls away as the land 47b gradually opens the exhaust port 49, so producing a gradually decreasing rate of engagement of the clutch. Instead of using valve lands of different diameters, the pipe 15 may be connected also to means employing a flexible diaphragm or a piston, the movement of which is transmitted to the valvemember 47. The clutch B may be engaged by increase of oil pressure, provided the centrifugal governor tends to open the oil-supply duct over which the smaller land of the valve moves. One land of the valve-member 183 of the valve L, Fig. 9, described below, is perforated to produce a similar effect to that obtainable with the valve-member 47. In order that the clutch may not disengage completely until the engine attains a speed lower than that at which clutch engagement begins, a spring- pressed bolt may engage a V-groove in the valve-member 47 at the point where it has been fully pressed to the right. In order that clutch engagement may begin only at a speed higher than normal when the starting load is heavy, a spring such as 55 under the control of the driver may bear on the valve-member 47 and on the low-speed-disengagement bolt, the bearing pressures being arranged either to maintain or not to maintain the sub-normal clutch-disengagement speed unaltered. The speed at which the clutch engages may be varied automatically with the throttle setting by employing a suction chamber 64 of which the diaphragm or piston 63 superimposes its effect on the spring 55, in this construction the low-speed-disengagement bolt being replaced by a lever 68 pivoted on an extension of the valve - member 47 and engaging a stationary notch 72. Controlling factors other than engine suction may be used. The valvemember 77 of the valve H employed during gear-change passes over an inlet port 90 and outlet passage 76, respectively supplied from and exhausting to the pump 1. During gearchange.the driver moves the gear lever to close temporarily a switch 78, Fig. 1, to lift a valve 82 in a chamber K to connect engine suction to a diaphragm chamber 86 to draw the valvemember 77 to the right against a light spring 89 to open the port 90 and close the passage 76 wholly or partly, oil pressure then passing through the port 49 in its valve G to disengage the main clutch wholly, to some extent, or not at all, the disengagement being greater with greater suction, i.e. with less throttle-opening. Air dash-pot means provides for slow reengagement of the clutch when the electric circuit is broken. The main clutch may be disengaged to give a free-engine effect when the accelerator pedal is released. In that position, provided the driver has moved a switch 96 to complete the necessary electrical circuit, engagement of contacts 97, 98 effects the raising of the valve 82 in the chamber K and the clutch is completely disengaged under maximum engine suction. To ensure, during a downward gear-change, complete clutch disengagement, to facilitate rapid engine acceleration, and clutch engagement only when the two main clutch elements are substantially in synchronism, a shaft 100 driven by the engine drives a casing 106 splined thereon at a speed slightly higher than that of a screw 105 which is driven bv a shaft 102 from the driven shaft 11 of the clutch. A ball 107 is spring-pressed through a hole in the casing to engage the screw 105 but to allow the ball to jump the threads if the casing is maintained at either end position. When the lower gear is engaged, the shaft 11 turns at an increased speed and the casing 106 moves to the right carrying with it a projection 112 which moves the valvemember 77 for complete clutch disengagement, even against any restraining action due to the effect of engine suction on the valve. A rod 111 on the projection 112 is connected to the throttle to speed up the engine as the clutch is disengaged, so that the casing 106 returns to the position shown to release the valve-member 77, allowing re-engagement of the two clutch members substantially at synchronism. Fig. 8 shows modified apparatus for clutch control during starting and stopping. The clutch is controlled by a rod 128 actuated both from a servomotor 130 connected to engine suction and by a servomotor 129 controlled from the valve G. A valve such as H may, however, be combined with the valve G to function on gearchange. A chamber such as K may be used in the suction line to the chamber 130. Fig. 9 shows the use of a single valve N to replace the speed-gear control-valves D<1>, E<1>, the arrangement being such that automatic control of the gear ratio according to the engine speed, together with the necessary main clutch operations both during starting and stopping and during speed changing are obtained. Separate governors may produce, through linkage, the movements of the valve-member 47 of the valve G, with which the valve H is associated, and of the valve-member 180 of the gear-controlling valve N, or alternatively a single governor 41 operates a valve-member 183 in a valve L which supplies oil to the ends of the valves G and N, of' which the first is effective only during clutch control at starting and stopping and the second at higher speeds. Movement of the valve-member 180 is resisted by a spring 189, adjustable by the driver, and by a ball 181 subject to the varying oil pressure, so as to control the speeds at which the gear is changed. Manual control for the valve 180 may be added. The Specification as open to inspection under Sect. 91 comprises also the following matter : Fig. 7 (Cancelled) shows an arrangement in which, during gear change, the clutch is controlled bv suction only for upward changes and by the synchronizer 106 &c. only for downward changes. Only when the casing 106 is moved to the right as the result of a speed of the clutch shaft 11 higher than that of the engine shaft, is a contact 118 made to allow current to flow to a coil 79<1> of which the armature 82<1> is then drawn to the right to operate the valve-member 77 for clutch disengagement. This circuit is further under the control of the speed-change knob 134 secured on a slidable and rotatable rod 135 and working in an inclined gate I ... IV. For changing down, the knob 134 is moved to the left, producing the required alterations in the gears D, E by way of the Bowden controls 132, 133 and also closing contacts 78, 78<1> to excite the contact 118. When the knob 134 is moved to the right for changing up, contacts 78, 78a, are closed and the valve K is actuated to control the main clutch by engine suction. The contact 78 is opened at the completion of each gear change to allow re-engagement of the clutch. The contacts 118 and the synchronizer 106 &c. may be omitted, in which case a dashpot slows the clutch re-engagement. In order that the spring 189 of Fig. 9 may be more easily controlled by the driver, it may act on a further valve which supplies fluid pressure, varying with the spring tension, to the end of the valve-member 180. The action of the spring and of the governor 41 may be applied to opposite ends of a single valve supplying pressure to opposite ends of the valve N, and in Fig. 12 (Cancelled), such a device is subject also to the inlet suction by adding the necessary chamber 209. A system of levers 203, 202, 205 receives the spring pressure, which is varied by movement of an abutment roller 204. In Fig. 8 (Cancelled) (not shown), two servomotors each controlled by a Bowden wire linked to the servomotor and to the control valve therefor may be operated by a selector lever each to effect two gear changes in a four-speed non- epicyclic gear. The valves are returned to normal position through the linkages by the movements of the servomotor pistons. In order to prevent the vehicle from running in a direction opposed to that determined by the driver's setting of the reversing-gear control knob 19, Fig. 1, the linka