US2910975A - Liquid fuel pumps for internal combustion engines - Google Patents

Description

Nov. 3, 1959 F. M. EVANS LIQUID FUEL PUMPS FOR INTERNAL comaus'rxon mamas Filed Feb. 20, 1958 United States Patent LIQUID FUEL PUTVIPS FOR INTERNAL COMBUSTIGN ENGINES Fraser Mackie Evans, Acton, London, England, assignor to C.A.V. Limited, London, Engiand Application February 20, 1958, Serial N 0. 716,313

Claims priority, application Great Britain February 22, 1957 2 Claims. (Cl. 123139) This invention relates to liquid fuel pumps for internal justable to vary with speed the instant at which injection commences, and an adjustable throttle for controlling the rate of supply of fuel from the feed pump to the injection pump. An example of this kind of pump is disclosed by Patent No. 2,660,992 (V. D. Roosa) It is characteristic of such a pump that the instant at which injection commences becomes progressively later with reduction of the quantity of fuel supplied by the injection pump and when the engine is running at idling speeds this becomes particularly objectionable.

The object of the invention is to provide in a convenient form a means for automatically advancing the instant of initiationof the discharge of the injection pump in each I cycle of action at idling speeds.

A device in'accordance with the invention comprises the combination of a cylinder associated with. the part containing the cam, a plunger slidable in the cylinder and connected to the cam, an abutment piece of larger di- 1 normally closed and spring loaded control valve.

in the example illustrated by the accompanying drawing, the angularly adjustable annular cam a of the injec tion pump (which latter comprises a pair of plungers b contained in a rotary cylinder c) is contained in a housing d on which is formed or secured a cylinder 2 which contains a slidable plnger f. In the latter is formed a lateral gap g which is occupied by one end of a short radial arm h, extending from the cam.

At one end the bore of the cylinder e is made of larger diameter than the part containing the plunger f, and in the said end is contained a slidable abutment i of pistonlike form, the movement of which in one direction is restricted by a stop formed by an annular shoulder k at the junction of the parts of the cylinder of diiferent diameter. Between the abutment and the adjacent end of the plunger is contained a spring m.

In the cylinder wall is formeda longitudinal passage it having between its ends an entrance'o for fuel supplied by the feed pump (not shown). At one end this passage leads through a non-retum valve-p to the end of the cylinder remote from the abutment i, this end of the cylinder being in communication with the housing d by way of a restricted passagewhich may be formed by a ice groove f in the plunger 1 or by a'peripheral clearance between this plunger and the adjacent part of the cylinder. At its other end it leads to the larger end of the cylinder through a control valve q which is loaded by a spring 1'; Also this end of the cylinder is in communication with the housing a by way of a restricted passage which may be formed by a peripheral clearance between the abutment i and the adjacent part of the cylinder, or by a restricted orifice s in the abutmentf The arrangement is such that while the engine is idling and the feed pump is supplyingfuel at a low pressure the plunger 1 is moved by pressure of the fuel on the end of the plunger remote from the spring m, so causing the cam to be moved in the direction for advancing the instant of discharge of the injection pump. When the engine speed is increased and the delivery pressure of the feed pump attains a given value, the increased pressure exerted by the fuel opens the control valve q and so causes fuel to enter also the adjacent end of the cylinder. The preponderating fuel pressure then acting on the abutment moves the latter and, through the spring m, causes the plunger to move in the direction for retarding the instant of discharge of the injection pump. When the abutment is arrested by the shoulder in the cylinder as shown in the drawing, continued increase of pressure of the fuel from the feed pump on the end of the plunger remote from the abutment, reverses the. direction of movement of the plunger and causes the instant of discharge of the injection pump to be advanced with increase of speed of the engine. I v

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. [In liquid fuel pump structure comprising an injection pump provided with a rotary member and at least one plunger slidable in a transverse bore in the rotary member for supplying liquid fuel to an internal combustion engine, a feed pump, an adjustable throttle for controlling the rate of supply of liquid fuel from the feed pump to the injection pump, and an adjustable cam for eifecting discharge of the injection pump, means for automatically varying the instant of discharge of the injection pump, which means comprise in combination a camadjusting plunger having an operative connection with the cam, a cylinder having a bore in which the plunger for receiving liquid fuel from the feed pump, an abutment piece of larger diameter than the plunger slidable in an enlarged extension of one end of the cylinder bore, a spring located between the plunger and abutment piece, a spring-loaded control valve which is situated between the cylinder passage and the outer end of the cylinder bore extension, and past which liquid fuel can flow from the passage to the said extension when the fuel pressure in the passage attains a predetermined value, and an unloaded non-return valve which is situated between the cylinder passage and the end of the cylinder bore remote from the said extension, and past which liquid fuel from the cylinder passage can flow to the cylinder bore.

2. A liquid fuel pump structure according to claim 1, and having between the cylinder bore and the enlarged extension thereof, a shoulder which serves by contact with the abutment piece to determine the extent of movement of the latter under the pressure of liquid fuel admitted to the outer end of the said extension.

References Cited in the file of this patent UNITED STATES PATENTS 2,660,992 Roosa Dec. 1, 1953

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