GB920010A - Vehicle transmission mechanism - Google Patents

Abstract

920,010. Hydraulic transmissions. JOSEPH LUCAS (INDUSTRIES) Ltd. April 4, 1961 [April 6, 1960; June 3, 1960], Nos. 12138/60 and 19684/60. Class 69 (2). [Also in Group XXXI] In a vehicle transmission wherein an enginedriven pump supplies liquid to two or more motors driving the vehicle wheels a restriction is provided in the individual flow line to each of the motors, and a throttle valve is movable in response to a predetermined increase in the pressure differential between the throat and the upstream side of the restriction to control the flow to the motor. All four wheels of the vehicle may be driven, the pump supplying liquid to two pairs of motors. As shown in Fig. 1, a restriction 4 is incorporated in a flow line 3 to a motor and the opposite ends of the restriction are connected through non-return valves 5 and 6 and pipe 7 to a compartment 11 of a chamber 8 divided into three compartments 11, 12 and 13 by diaphragms 9 and 10. The narrow part of the restriction is connected to the chamber 13 and the pipe 7 is connected through a restriction 14 to the chamber 12 to allow escape of liquid from chamber 11. The compartment 12 is connected to a reservoir through a pipe 23. A throttle valve 15 is incorporated in flow line 3 and comprises a conical portion and a portion of larger diameter working in a cylinder 16 connected by a passage 17 to chamber 12 under the control of a member 19. A coil spring 20 bears against diaphragm 10 normally holding the closure member 19 open and is adjusted by a cam 22. The valve 15 has a restricted passage 18. If the pressure differential between the throat of the restriction and the upstream side is sufficient to overcome the action of spring 20, the closure member 19 closes line 17 and pressure builds up in cylinder 16, moving the valve 15 whereby the flow of liquid to the motor is restricted. The device prevents undue consumption of liquid by a motor connected to a wheel which develops spin. The cam 22 may be connected to the variable inclination swash-plate of the pump to determine the angular velocity at which the control becomes effective. In a modification, Fig. 2, the opposite sides of a restriction 4 in the flow line 3 to a motor are connected to the end of a chamber 24 beneath a piston 29. A compartment 26, which contains a shuttle valve 30 shown in its normal position, is connected through a restricted orifice 33 to the compartment beneath the piston 29. The flow tube 3, downstream of the restriction 4, enters and leaves a chamber 34 containing a double piston device 37 which, in the normal position shown, does not obstruct flow. The opposite ends of chamber 34 are connected with compartment 26 so as to normally register with grooves 35 and 36 in the shuttle 30 which also has an annular groove 32 so as not to obstruct the connection through restriction 33 in all positions of the shuttle. A spring 31 bears upon piston 28. When the pressure differential across the flow orifice 4 exceeds a predetermined valve, the shuttle 30 moves against the action of spring 31, which is preloaded by a cam 40, to connect one side of the piston 37 to the annular groove 32 and the other side of the piston 37 to a compartment 25 of the chamber 24 which communicates with a reservoir 39 whereby the piston 37 is moved in a direction to restrict flow through the line 3.