Throttle valve positioner

Claim 1

A throttle valve positioner in combination with an internal combustion engine having an air intake and a throttle valve provided in said air intake, said throttle valve positioner comprising: a stopper provided adjacent said throttle valve for varying the position of said throttle valve and coupled to said throttle valve via a first adjustment means; a means for normally operating said throttle valve; a first vacuum bleed port provided in said air intake at a point downstream from said throttle valve when said engine is idling and upstream from said throttle valve when said engine is running at a steady speed; a throttle valve positioner diaphragm device mechanically coupled to said stopper for moving said stopper in response to a vacuum at said first vacuum bleed port, said diaphragm device comprising a casing having first and second ends and an opening in each of said ends, a diaphragm dividing said casing and defining a chamber between said first end and said diaphragm and a spring biasing said diaphragm away from said first end and wherein said opening in said first end is coupled to said first vacuum bleed port by a first conduit and wherein said stopper is mechanically connected to said diaphragm via said opening in said second end; a means for delaying the response of said throttle valve positioner diaphragm device to a change in vacuum at said first vacuum bleed port provided in said first conduit, said delay means comprising a flow restricting means having such a structure that the flow rate of fluid from said first vacuum bleed port toward said diaphragm chamber is greater than that in the reverse direction and further comprises a pair of flow restricting means arranged in parallel with each other, and a check valve disposed in series with one of said flow restricting means, said check valve permitting solely the flow of fluid from said first vacuum bleed port toward said chamber of said diaphragm device; a second vacuum bleed port provided in said air intake at a point which is always downstream of said throttle valve; and a vacuum control valve for fixing the vacuum of said first vacuum bleed port at atmospheric pressure whenever a vacuum at said second vacuum bleed port is greater than a predetermined value, said vacuum control valve comprising: a casing having an open end communicating with the atmosphere; a diaphragm provided within said casing with the outer periphery thereof brought into fluid-tight engagement with the inner wall of said casing and defining a chamber therein; a branch conduit extending at one end thereof into said open end of said casing and connected at the other end thereof to said chamber of said throttle valve positioner diaphragm device; a valve member mounted to said diaphragm for openably closing said end of said branch conduit extending into said casing; biasing means for normally biasing said diaphragm in a direction in which said end of said branch conduit extending into said casing is closed by said valve member, said biasing means being disposed between said diaphragm and said casing, and the biasing pressure thereof being adjusted as desired by adjustment means, said adjustment means comprising a screw in screw threaded engagement with said casing; a filler provided in the space formed between the rear end of said screw and said casing for inhibiting inflow of positive pressure into said vacuum control valve diaphragm chamber through the screw threads; and another conduit for admitting the vacuum at said second vacuum bleed port into said vacuum control valve diaphragm chamber.