GB1564114A

GB1564114A - Liquid fuel pumping apparatus

Info

Publication number: GB1564114A
Application number: GB3947575A
Authority: GB
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1975-09-26
Filing date: 1975-09-26
Publication date: 1980-04-02
Also published as: FR2325809A1; FR2325809B1

Description

(54) LIQUID FUEL PUMPING APPARATUS (71) We, CAV Limited, a British Company of Well Street, Birmingham, B19 2XF do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:: This invention relates to liquid fuel pumping apparatus for supplying fuel to internal combustion engines and of the kind comprising an injection pump driven in timed relationship with the associated engine, a feed pump for supplying fuel under pressure to the injection pump at a pressure which varies in accordance with the speed at which the apparatus is driven, a throttle member for controlling the quantity of fuel supplied to the injection pump and thereby controlling the quantity of fuel supplied to the associated engine and fluid pressure operable means for controlling the timing of delivery of fuel by the injection pump.

The object of the invention is to provide such an apparatus in a simple and convenient form.

According to the invention in a fuel injection pumping apparatus of the kind specified said fluid pressure operable means comprises a fluid pressure operable piston which is movable against the action of resilient means to advance the timing of injection of fuel to the engine, the piston being movable by fuel under pressure from the outlet of the feed pump, a fluid pressure operable member movable against the action of further resilient means between an operative and an inoperative position, said member when the apparatus is at rest being in the operative position and holding said piston in a position so that the timing of injection of fuel is correct for starting the engine, said member in the inoperative position imposing no restraint on the piston, said member when fluid pressure is applied thereto moving in the opposite direction to the direction of movement of the piston against the action of its resilient means, the member constituting a reaction member for the resilient means loading the piston.

One example of a fuel injection pumping apparatus in accordance with the invention will now be described with reference to the accompanying drawing which shows the apparatus in diagrammatic form.

With reference to the drawings, the apparatus comprises an injection pump 10 to which fuel under pressure is supplied by way of a throttle member 11 from the outlet of a feed pump 12. The feed pump has an inlet 13 which is connected to a source of fuel and interconnecting the inlet and the outlet of the feed pump is a valve 14 which controls the outlet pressure of the feed pump so that it varies in accordance with the speed at which the associated engine is operating. The setting of the throttle 11 is determined in part by the operator of the associated engine and in part by a governor responsive to the speed at which the engine is operating.

The injection pump in known manner, comprises a rotary member driven in timed relationship with the associated engine, there being provided in the rotary member a transversely extending bore in which is mounted a pair of reciprocable pumping plungers. The plungers are moved inwardly as the rotary member rotates, by the action of cam lobes formed on the internal periphery of an annular cam ring. As is the usual practice, the plungers are acted upon by shoes which in turn carry rollers engaging the cam lobes. The angular position of the annular cam determines the timing of injection of fuel and the cam is positioned by means of a fluid pressure operable piston 15 which is located in a cylinder 16. The end of the cylinder is closed by a plug 17 and a conduit 18 is provided through which fuel from the outlet of the feed pump can flow to the cylinder to act upon the piston 15.The conduit incorporates a non-return valve 19 which is by-passed by a restrictor 20.

The piston 15 has a piston rod or extension 21 formed integrally therewith and this is slidable axially within a collar 22.

Also provided is a further cylinder 23 in which is mounted a fluid pressure operable member 24. The member 24 is spring loaded by means of a coiled compression spring 25 in a direction away from the piston 15.

Moreover, the member 24 defines a bore in which is slidably mounted a piston element 26. The piston element 26 engages the collar under the action of a coiled compression spring 27 disposed intermediate the element and the fluid pressure operable member.

Moreover, supported in the inner peripheral wall of the fluid pressure operable member 24 is a circlip 28 and located intermediate the circlip and the collar 22 is a spacer element 29. Disposed intermediate the collar 22 and the piston 15 is a pair of springs 30.

Surrounding the spring 25 and enclosing the end of the fluid pressure operable member is a cap 31 and the space within the cap 31 is connected to the outlet of the feed pump 12 by way of a conduit 32. Moreover, the space surrounding the spring 27 is connected by way of a passage in the wall of the member 24 and a further passage in the wall of the cylinder 23, with a point intermediate a pair of variable restrictors 33, 34 connected in series. The upstream side of the restrictor 33 is connected to the outlet of the feed pump 12 and the downstream side of the restrictor 34 communicates with a drain conveniently the inlet of the feed pump. Both restrictors 33 and 34 are variable and are arranged to vary in accordance with the setting of the throttle 11.

The extension 21 as previously stated, extends through the collar and is provided with a washer whereby when the apparatus is at rest the spring 25 displaces the fluid pressure operable member 24 its maximum extent to its operative position in which it contacts the cap 31, the washer being engaged by the collar so that the piston 15 is positioned to provide the required timing of injection for starting the engine. The direction of rotation of the distributor member is indicated by the arrow A.

When the engine starts the pressure at the outlet of the feed pump increases and the member 24 is moved against the action of the spring 25 to its inoperative position in which it is in contact with a step defined at the end of the cylinder 23. During this movement the piston 15 will move towards the end of the cylinder 16 and the timing of delivery of fuel is retarded. However, as the pressure of fuel applied to the piston 15 increases it will move against the action of the springs 30 to advance the timing of delivery with increasing speed. During such movement the piston rod 21 moves freely within the collar 22. It will be apparent that the springs 30 and 27 are effectively in series and certain movement of the spring 27 will also take place.The force applied to the piston element 26 by the spring 27 is supplemented by the pressure of fuel intermediate the restrictors 33 and 34 so that the piston element 26 will assume a position which depends upon the load on the associated engine. As the load increases and therefore more fuel is supplied to the engine, the piston 26 will be moved towards the right to slightly retard the timing of injection of fuel.

By the arrangement described the spring biasing the fluid pressure operable member 24 does not have to overcome the effect of the springs 27 and 30 when moving the member 24 from its inoperative position to its operative position, and therefore a relatively low rate spring can be used. Moreover, the advance device i.e. the fluid pressure operable means is compact since the fluid pressure operable member 24 surrounds at least part of the device which would normally be provided.

WHAT WE CLAIM IS: 1. A fuel injection pumping apparatus of the kind specified in which said fluid pressure operable means comprises a fluid pressure operable piston which is movable against the action of resilient means to advance the timing of injection of fuel to the engine, the piston being movable by fuel under pressure from the outlet of the feed pump, a fluid pressure operable member movable against the action of further resilient means between an operative and an inoperative position, said member when the apparatus is at rest being in the operative position and holding said piston in a position so that the timing of injection of fuel is correct for starting the engine, said member in the inoperative position imposing no restraint on the piston, said member when fluid pressure is applied thereto moving in the opposite direction to the direction of movement of the piston against the action of its resilient means, the member constituting a reaction member for the resilient means loading the piston.

2. An apparatus according to claim 1 in which said resiliently loaded member is of cup-shaped form and surrounds at least part of an extension of said piston, and abutment means defined on the piston and member, said abutment means acting to position the piston when the member is in the operative position.

3. An apparatus according to claim 1 in which said abutment means comprises a collar mounted on said extension and a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the cylinder to act upon the piston 15. The conduit incorporates a non-return valve 19 which is by-passed by a restrictor 20. The piston 15 has a piston rod or extension 21 formed integrally therewith and this is slidable axially within a collar 22. Also provided is a further cylinder 23 in which is mounted a fluid pressure operable member 24. The member 24 is spring loaded by means of a coiled compression spring 25 in a direction away from the piston 15. Moreover, the member 24 defines a bore in which is slidably mounted a piston element 26. The piston element 26 engages the collar under the action of a coiled compression spring 27 disposed intermediate the element and the fluid pressure operable member. Moreover, supported in the inner peripheral wall of the fluid pressure operable member 24 is a circlip 28 and located intermediate the circlip and the collar 22 is a spacer element 29. Disposed intermediate the collar 22 and the piston 15 is a pair of springs 30. Surrounding the spring 25 and enclosing the end of the fluid pressure operable member is a cap 31 and the space within the cap 31 is connected to the outlet of the feed pump 12 by way of a conduit 32. Moreover, the space surrounding the spring 27 is connected by way of a passage in the wall of the member 24 and a further passage in the wall of the cylinder 23, with a point intermediate a pair of variable restrictors 33, 34 connected in series. The upstream side of the restrictor 33 is connected to the outlet of the feed pump 12 and the downstream side of the restrictor 34 communicates with a drain conveniently the inlet of the feed pump. Both restrictors 33 and 34 are variable and are arranged to vary in accordance with the setting of the throttle 11. The extension 21 as previously stated, extends through the collar and is provided with a washer whereby when the apparatus is at rest the spring 25 displaces the fluid pressure operable member 24 its maximum extent to its operative position in which it contacts the cap 31, the washer being engaged by the collar so that the piston 15 is positioned to provide the required timing of injection for starting the engine. The direction of rotation of the distributor member is indicated by the arrow A. When the engine starts the pressure at the outlet of the feed pump increases and the member 24 is moved against the action of the spring 25 to its inoperative position in which it is in contact with a step defined at the end of the cylinder 23. During this movement the piston 15 will move towards the end of the cylinder 16 and the timing of delivery of fuel is retarded. However, as the pressure of fuel applied to the piston 15 increases it will move against the action of the springs 30 to advance the timing of delivery with increasing speed. During such movement the piston rod 21 moves freely within the collar 22. It will be apparent that the springs 30 and 27 are effectively in series and certain movement of the spring 27 will also take place.The force applied to the piston element 26 by the spring 27 is supplemented by the pressure of fuel intermediate the restrictors 33 and 34 so that the piston element 26 will assume a position which depends upon the load on the associated engine. As the load increases and therefore more fuel is supplied to the engine, the piston 26 will be moved towards the right to slightly retard the timing of injection of fuel. By the arrangement described the spring biasing the fluid pressure operable member 24 does not have to overcome the effect of the springs 27 and 30 when moving the member 24 from its inoperative position to its operative position, and therefore a relatively low rate spring can be used. Moreover, the advance device i.e. the fluid pressure operable means is compact since the fluid pressure operable member 24 surrounds at least part of the device which would normally be provided. WHAT WE CLAIM IS:

1. A fuel injection pumping apparatus of the kind specified in which said fluid pressure operable means comprises a fluid pressure operable piston which is movable against the action of resilient means to advance the timing of injection of fuel to the engine, the piston being movable by fuel under pressure from the outlet of the feed pump, a fluid pressure operable member movable against the action of further resilient means between an operative and an inoperative position, said member when the apparatus is at rest being in the operative position and holding said piston in a position so that the timing of injection of fuel is correct for starting the engine, said member in the inoperative position imposing no restraint on the piston, said member when fluid pressure is applied thereto moving in the opposite direction to the direction of movement of the piston against the action of its resilient means, the member constituting a reaction member for the resilient means loading the piston.

projection on the inner surface of the wall of the member.

4. An apparatus according to claim 3 in which said resiliently loaded member defines a cylinder, a further piston located in said cylinder, said collar engaging said further piston, said resilient means comprising a first spring acting intermediate the further piston and the base wall of the member and a second spring or springs biasing said first mentioned piston relative to said further piston and the collar being slidable relative to the extension, whereby with an increase in the fuel pressure acting upon said first mentioned piston the springs will be compressed by movement of the first mentioned piston in the direction to advance the timing of delivery of fuel.

5. An apparatus according to claim 4 in which said second spring or springs is/are disposed intermediate the collar and said first mentioned piston.

6. An apparatus according to claim 5 including passage means for admitting fluid under pressure to said cylinder, said fluid under pressure assisting the action of said first spring and means for varying the pressure of said fluid so that it varies in accordance with the setting of said throttle member.

7. An apparatus according to claim 6 in which said fluid under pressure is derived from a point intermediate a pair of restrictors connected in series between the outlet of the feed pump and a drain, the restriction offered by said restrictors being variable in accordance with the setting of the throttle member.

8. An apparatus according to claim 6 in which said extension at its end remote from the main body of the piston is provided with a circlip engageable by the collar.

9. A fuel injection pumping apparatus substantially as hereinbefore described with reference to the accompanying drawing.