GB1585360A

GB1585360A - Fuel injection pump

Info

Publication number: GB1585360A
Application number: GB44679/77A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1976-10-29
Filing date: 1977-10-27
Publication date: 1981-03-04
Also published as: JPS5356418A; SE7712105L; BR7707228A; FR2369430A1; DE2649287A1

Description

(54) A FUEL INJECTION PUMP (71) We, ROBERT BOSCH GMBH. a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, 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: Fuel injection pumps are known which comprise a block-like housing accommodating a suction and a pressure valve which operate with compression springs. The block-like housing is clamped firmly, by a connecting fitting in the pump housing, directly as an axial termination of the pump working chamber. A suction chamber of the pump at least partially surrounds the block-like housing radially.

In a known fuel injection pump of this type, the pump working chamber is directly connected to the spring chamber of the suction valve so that the dead space of the pump working chamber is substantially increased. The size of the dead space is, however, extremely important for the cyclical quantity distribution. Since fuel is to a certain degree compressible, the supply efficiency of the pump varies speeddependently with a large dead space.

According to the present invention there is provided a fuel injection pump for an internal combustion engine comprising at least one pump piston, movable in a cylinder disposed in a housing of the fuel injection pump, a working chamber located in the cylinder, a pressure valve and a suction valve both disposed in a block-like housing and both comprising a valve closure member, biased by a compression spring towards a co-operating valve seat, both said closure members opening and closing along axes parallel to the axis of the working chamber, said block-like housing being divided along a plane at right angles to the axis of the working chamber and being clamped by means of a pressure connecting fitting which is inserted into the housing of the fuel injection pump from the outside in such a manner that the cylinder is sealed and the working chamber is thereby formed, the suction valve being connected to a suction chamber, which is enclosed in the housing of the fuel injection pump and at least partially surrounds the block-like housing radially, and the pressure valve being connected to a pressure bore of the pressure connecting fitting downstream of the closure member.

The fuel injection pump according to the present invention has, by comparison with the above mentioned known pump, the advantage that the dead space may be reduced to a minimum which results in a substantial increase in supply efficiency.

Moreover, the fluctuation in this quantity of fuel injection at the different supply strokes of the pump piston, which fluctuation is very disadvantageous in such a pump, is reduced to a minimum. Another advantage is that the stroke of the pump piston may extend virtually to the end of the working chamber which is thus evacuated during a warm start and thus because of the small space fuel is supplied as soon as the pump starts.

The present invention will hereinafter be further described by way of example with reference to the accompanying drawings in which : - Figure 1 is a longitudinal section of a fuel injection pump constructed in accordance with the present invention, and Figure 2 is a detail of Figure 1 showing the valve block in longitudinal section.

In a housing 1 of a particularly small fuel injection pump, which is preferably used for direct injection of stratified injection quantities in Otto engines, a cam shaft 2 is supported which drives pump pistons 3 against the force of springs 4.

The housing 1 is closed in the region of the end of camshaft 2 by a lid 5. Also disposed in the housing 1 is a suction chamber 6 which is supplied with fuel by a preliminary supply pump (not shown) and in which block-like housings 7 are disposed, said block-like housings being clamped firmly in position by pressure connecting fittings 8 and in this position cover the pump working chambers 9.

Pressure lines (not shown) lead from the connecting fittings 8 to the engine. O-rings 10 are disposed between the connecting fittings 8 and the housing 1. The chamber 11 in the housing 1 accommodating the camshaft 2 is connected by a connection opening 12 in the lid 5 to a lubricant source and is externally sealed on the drive side of the camshaft 2 by a radial seal 13 disposed between the camshaft 2 and the housing 1. For lubricating the camshaft bearings 14 and 15, the camshaft has a blind axial bore 16 from which radial bores 17 and 18 conduct lubricant to the bearings.

By way of a groove 19 in the lid 5 the lubricant also passes into a bore 20 which is disposed perpendicular to the pump pistons 3 and intersects the bores in which said pistons 3 reciprocate. Annular grooves 21 are provided on the pump pistons 3 in the region of intersection so that apart from the lubricating action for the pistons 3 there is an additional fuel block or removal of leaking fuel from the working chambers.

Figure 2 shows one of the connecting fittings 8 and one of the block-like housings 7 to an enlarged scale and the latter in longitudinal section. The block-like housing 7 comprises a base plate 23 and a block housing 24 disposed above it. The plate 23 and the housing 24 are pressed onto one another between the surface 25 in the suction chamber 6 and the connecting fitting 8 which is screwed into the housing 1. A sealing plate 26 is disposed between the base plate 23 and the surface 25.

A suction valve 27 and a pressure valve 28 are disposed in the block-like housing 7.

The movable valve member 29 of the suction valve has two ends of which one end 30 has a part spherical surface which engages a correspondingly shaped portion of a washer 31 while the other end 32 has a part spherical surface which cooperates with a correspondingly shaped valve seat 33 provided on the base plate 23. A compression spring 34 is disposed between the washer 31 and the base plate 23 and has the effect that the valve member end 32 is urged onto the seat 33. The individual suction valve parts are disposed in a chamber 35 of the block housing 24 which has a radial opening 36 connecting it to the suction chamber 6. During the suction stroke of the pump piston 3 (i.e.

the downward stroke as viewed in Figure 1), the valve member 29 is displaced against the force of the spring 34 off the valve seat 33 and allows a connection between the suction chamber 6 and the pump working chamber 9. The stroke of the valve member 29 is limited by the sealing plate 26 which serves simultaneously as a stop. The annular cross-sectional area of passage which is exposed when the suction valve 27 opens is relatively great despite a small stroke. Because of the described construction, the dead space seen from the pump working chamber 9 is reduced to a minimum, in particular in that the chamber 35 accommodating the spring 34 is not connected during the pressure stroke (i.e. the upward stroke as viewed in Figure 1) of the pump piston 3 to the pump working chamber 9.

The pressure valve 28 is in the form of a plate valve having a valve plate 38 which is displaced against a compression spring 39 during the pressure stroke of the pump piston. The valve plate 38 co-operates with an annular valve seat 41 produced by cutting inner and outer recesses 40 in the base plate so that a relatively small and therefore readily workable sealing surface is produced therebetween. The inner recess 40 is connected by a bore 42 to the pump working chamber 9. Here too, the clearance facing the pump working chamber 9 is cut to a minimum, because the pump piston 3 in this construction may advance during its pressure stroke almost up to the base plate 23. The fuel then passes from the chamber 43 accommodating the spring 39 and disposed in the block housing 24 during the pressure stroke by way of a bore 45 into a pressure bore 46 disposed in the fitting 8.

The form of the block-like housing 7 has in particular the advantage that when the valves are no longer working efficiently it is possible to exchange the entire block-like housing relatively easily. Furthermore, even if the movable valve part 29 of the suction valve breaks, no damage can be caused by a valve part falling into the pump working chamber 9.

WHAT WE CLAIM IS: 1. A fuel injection pump for an internal combustion engine comprising at least one pump piston, movable in a cylinder disposed in a housing of the fuel injection pump, a working chamber located in the cylinder, a pressure valve and a suction valve both disposed in a block-like housing and both comprising a valve closure member biased by a compression spring towards a co-operating valve seat, both said closure members opening and closing along axes parallel to the axis of the working chamber, said block-like housing being divided along a plane at right angles to the axis of the working chamber and being clamped by means of a pressure connecting fitting which is inserted into the housing of the fuel injection pump from the outside in such a manner that the cylinder is sealed and the working chamber is thereby formed,

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. connecting fittings 8 and in this position cover the pump working chambers 9. Pressure lines (not shown) lead from the connecting fittings 8 to the engine. O-rings 10 are disposed between the connecting fittings 8 and the housing 1. The chamber 11 in the housing 1 accommodating the camshaft 2 is connected by a connection opening 12 in the lid 5 to a lubricant source and is externally sealed on the drive side of the camshaft 2 by a radial seal 13 disposed between the camshaft 2 and the housing 1. For lubricating the camshaft bearings 14 and 15, the camshaft has a blind axial bore 16 from which radial bores 17 and 18 conduct lubricant to the bearings. By way of a groove 19 in the lid 5 the lubricant also passes into a bore 20 which is disposed perpendicular to the pump pistons 3 and intersects the bores in which said pistons 3 reciprocate. Annular grooves 21 are provided on the pump pistons 3 in the region of intersection so that apart from the lubricating action for the pistons 3 there is an additional fuel block or removal of leaking fuel from the working chambers. Figure 2 shows one of the connecting fittings 8 and one of the block-like housings 7 to an enlarged scale and the latter in longitudinal section. The block-like housing 7 comprises a base plate 23 and a block housing 24 disposed above it. The plate 23 and the housing 24 are pressed onto one another between the surface 25 in the suction chamber 6 and the connecting fitting 8 which is screwed into the housing 1. A sealing plate 26 is disposed between the base plate 23 and the surface 25. A suction valve 27 and a pressure valve 28 are disposed in the block-like housing 7. The movable valve member 29 of the suction valve has two ends of which one end 30 has a part spherical surface which engages a correspondingly shaped portion of a washer 31 while the other end 32 has a part spherical surface which cooperates with a correspondingly shaped valve seat 33 provided on the base plate 23. A compression spring 34 is disposed between the washer 31 and the base plate 23 and has the effect that the valve member end 32 is urged onto the seat 33. The individual suction valve parts are disposed in a chamber 35 of the block housing 24 which has a radial opening 36 connecting it to the suction chamber 6. During the suction stroke of the pump piston 3 (i.e. the downward stroke as viewed in Figure 1), the valve member 29 is displaced against the force of the spring 34 off the valve seat 33 and allows a connection between the suction chamber 6 and the pump working chamber 9. The stroke of the valve member 29 is limited by the sealing plate 26 which serves simultaneously as a stop. The annular cross-sectional area of passage which is exposed when the suction valve 27 opens is relatively great despite a small stroke. Because of the described construction, the dead space seen from the pump working chamber 9 is reduced to a minimum, in particular in that the chamber 35 accommodating the spring 34 is not connected during the pressure stroke (i.e. the upward stroke as viewed in Figure 1) of the pump piston 3 to the pump working chamber 9. The pressure valve 28 is in the form of a plate valve having a valve plate 38 which is displaced against a compression spring 39 during the pressure stroke of the pump piston. The valve plate 38 co-operates with an annular valve seat 41 produced by cutting inner and outer recesses 40 in the base plate so that a relatively small and therefore readily workable sealing surface is produced therebetween. The inner recess 40 is connected by a bore 42 to the pump working chamber 9. Here too, the clearance facing the pump working chamber 9 is cut to a minimum, because the pump piston 3 in this construction may advance during its pressure stroke almost up to the base plate 23. The fuel then passes from the chamber 43 accommodating the spring 39 and disposed in the block housing 24 during the pressure stroke by way of a bore 45 into a pressure bore 46 disposed in the fitting 8. The form of the block-like housing 7 has in particular the advantage that when the valves are no longer working efficiently it is possible to exchange the entire block-like housing relatively easily. Furthermore, even if the movable valve part 29 of the suction valve breaks, no damage can be caused by a valve part falling into the pump working chamber 9. WHAT WE CLAIM IS:

1. A fuel injection pump for an internal combustion engine comprising at least one pump piston, movable in a cylinder disposed in a housing of the fuel injection pump, a working chamber located in the cylinder, a pressure valve and a suction valve both disposed in a block-like housing and both comprising a valve closure member biased by a compression spring towards a co-operating valve seat, both said closure members opening and closing along axes parallel to the axis of the working chamber, said block-like housing being divided along a plane at right angles to the axis of the working chamber and being clamped by means of a pressure connecting fitting which is inserted into the housing of the fuel injection pump from the outside in such a manner that the cylinder is sealed and the working chamber is thereby formed,

the suction valve being connected to a suction chamber, which is enclosed in the housing of the fuel injection pump and at least partially surrounds the block-like housing radially, and the pressure valve being connected to a pressure bore of the pressure connecting fitting downstream of the closure member.

2. A fuel injection pump as claimed in claim 1, in which the block-like housing is divided along said plane, into a base plate carrying the valve seats and a block housing defining chambers which accommodate the compression springs.

3. A fuel injection pump as claimed in claim 2, in which the suction valve opens towards the pump working chamber and has a valve member urged towards its valve seat by its compression spring which spring acts between the base plate and a washer located on the valve member.

4. A fuel injection pump as claimed in claim 3, in which the contacting surfaces between the washer and the valve member and/or the contacting surfaces between the valve seat and the valve member are of part spherical shape.

5. A fuel injection pump as claimed in any preceding claim in which the pressure valve is a plate valve.

6. A fuel injection pump as claimed in claim 5, in which a pressure bore in the base plate opens out upstream of the valve plate eccentrically thereto into a flat chamber covered by the valve plate.

7. A fuel injection pump as claimed in any preceding claim in which the connecting fitting serves as a screw nipple for a pressure delivery line.

8. A fuel injection pump as claimed in any preceding claim which comprises a plurality of said pump pistons and cylinders which lie adjacent to each other in series each with a said pressure valve and a said suction valve and in which the suction chambers are connected one to another.

9. A fuel injection pump constructed and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.