Fuel pump

Abstract

A fuel pump for conveying fuel includes a conveying unit having a cylinder, a plunger received in the cylinder, a pump spring received in the cylinder, an inner sleeve connected to the plunger, an outer sleeve in contact with the pump spring and in contact with a roller of a cam mechanism, and a locking bolt configured to detachably connect the inner and outer sleeves.

Claims

1. A fuel pump for conveying fuel, comprising a conveying unit including a cylinder, a plunger received in the cylinder, a pump spring received in the cylinder, an inner sleeve connected to the plunger, an outer sleeve in contact with the pump spring and in contact with a roller of a cam mechanism, and a locking bolt configured to detachably connect the inner and outer sleeves, wherein the locking bolt is biased by a locking spring located above the locking bolt, wherein the plunger moves in the cylinder at a delivery stroke, a level of which is variable by the cam mechanism.

2. The fuel pump of claim 1, wherein the inner and outer sleeves are connected to one another in a base position of the locking bolt, and the inner and outer sleeve are detached from one another in a rest position of the locking bolt.

3. The fuel pump of claim 2, wherein the locking spring is configured to bias the locking bolt in a direction of the base position, said locking spring capable of being acted upon by engine oil under pressure such that the locking spring is pushed into the inner sleeve and the locking bolt is moved to the rest position, when a force applied on the locking spring by the pressure of the engine oil exceeds a limit value to thereby cause a detachment between the inner and outer sleeves.

4. The fuel pump of claim 1, wherein the conveying unit is configured to deliver fuel only when the inner and outer sleeves are connected to one another, and to interrupt delivery of fuel when the inner and outer sleeves are detached from one another.

5. An injection system for a combustion engine, comprising: a module including a fuel pump for conveying fuel, said fuel pump including a conveying unit including a cylinder, a plunger received in the cylinder, a pump spring received in the cylinder, an inner sleeve connected to the plunger, an outer sleeve in contact with the pump spring and in contact with a roller of a cam mechanism, and a locking bolt configured to detachably connect the inner and outer sleeves, wherein the locking bolt is biased by a locking spring located above the locking bolt; and a fuel accumulator operably connected to the fuel pump of the module, wherein the plunger moves in the cylinder at a delivery stroke, a level of which is variable by the cam mechanism.

6. The injection system of claim 5, wherein the conveying unit is configured to deliver fuel only when the locking bolt assumes a base position, and to interrupt delivery of fuel when the locking bolt assumes a rest position.

7. The injection system of claim 5, wherein the inner and outer sleeves are connected to one another in a base position of the locking bolt, and the inner and outer sleeve are detached from one another in a rest position of the locking bolt.

8. The injection system of claim 7, wherein the locking spring is configured to bias the locking bolt in a direction of the base position, said locking spring capable of being acted upon by engine oil under pressure such that the locking spring is pushed into the inner sleeve and the locking bolt is moved to the rest position, when a force applied on the locking spring by the pressure of the engine oil exceeds a limit value to thereby cause a detachment between the inner and outer sleeves.

9. The injection system of claim 5, wherein the conveying unit is configured to deliver fuel only when the inner and outer sleeves are connected to one another, and to interrupt delivery of fuel when the inner and outer sleeves are detached from one another.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawings.

(2) FIG. 1 is a schematic sectional view of a fuel pump according to the present invention showing a locking bolt in a base position; and

(3) FIG. 2 is a schematic sectional view of a fuel pump according to the present invention showing a locking bolt in a rest position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) The depicted embodiment is to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the FIGURE may not necessarily be to scale. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

(5) Turning now to FIG. 1, there is shown a schematic sectional view of a fuel pump according to the present invention, generally designated by reference numeral 2. The fuel pump 2 includes a housing 4 which accommodates a cylinder 6 of a conveying unit. It will be appreciated by persons skilled in the art that the conveying unit contains further mechanical apparatus which has been omitted from FIG. 1 for the sake of simplicity. A plunger 8 or tappet of the fuel pump 2 is arranged for reciprocal movement within the cylinder 6 and is embraced by a pump spring 10 which is also arranged within the cylinder 6 and extends between a shoulder 11 of a connection module 20 and a top surface of an outer sleeve 14. The outer sleeve 14 is arranged in coaxial surrounding relation to an inner sleeve 12 and detachably connected to the inner sleeve 12 via a locking bolt 16. The plunger 8 is connected to the inner sleeve 12, whereas the outer sleeve 14 is connected at one end to the pump spring 10 and at the other end to a roller 18. The roller 18 represents a component of a cam mechanism 34, although it may also be considered as a component of the fuel pump 2, depending on the definition being applied.

(6) The connection module 20 of the fuel pump 2 has a first inlet port 22 and a second inlet port 24, with one of the ports 22, 23 being configured for delivery of fuel to the conveying unit. The other one of the ports 22, 24 is configured to deliver fuel, which is pressurized by the plunger 8 in the cylinder 6 of the conveying unit, to a fuel accumulator from where fuel under pressure is delivered to downstream fuel injectors for injection of fuel into combustion chambers of a combustion engine. The fuel pump 2 and the fuel accumulator thus represent components of an injection system of the combustion engine.

(7) As the fuel pump 2 pressurizes fuel, it is also referred to as high-pressure pump.

(8) The inner sleeve 12 and the outer sleeve 14 of the fuel pump 2 are either coupled to one another or decoupled from one another via the locking bolt 16. The locking bolt 16 is biased by a locking spring 28 for movement in relation to the inner and outer sleeves 12, 14 between a base position 30, also referred to as locking position, as illustrated in FIG. 1 and a rest position 32, as illustrated in FIG. 2.

(9) In the base position 30, the locking bolt 16 is biased by the locking spring 28 into engagement with the inner and outer sleeves 12, 14 so that the inner and outer sleeves 12, 14 are connected to one another. The inner and outer sleeves 12, 14 form hereby a mechanically interconnected unitary structure, with the plunger 8 and the roller 18 being mechanically connected to one another via the unitary structure of the inner and outer sleeves 12, 14. A cam of the cam mechanism 34 is in contact with the roller 18 so that a rotation of the cam is transferred via the roller 18 and the inner and outer sleeves 12, 14 onto the plunger 8 to thereby cause the plunger 8 to move within the cylinder 6. As a result, fuel is delivered via one of the ports 22, 24 to the conveying unit and pressurized by the moving plunger 8 for further delivery to the fuel accumulator.

(10) The injection system thus includes the fuel pump 2 and one or more conveying units, each conveying unit having a plunger 8 that can be activated or can be idle. During operation of the combustion engine, it is therefore possible to reduce an amount of fuel that has been pressurized in the fuel accumulator for injection into a combustion chamber of the combustion engine.

(11) Depending on the demand of fuel, at least one conveying unit of the fuel pump 2 can be switched off. For this purpose, provision is made for the locking bolt 16 to be moved from the base position 30, as shown in FIG. 1, into the rest position 32, as shown in FIG. 2, in opposition to the force applied by the locking spring 28 upon the locking bolt 16. The locking spring 28 is hereby acted upon by engine oil which applies a force, generated by the pressure of the engine oil and opposing the force applied by the locking spring 28 upon the locking bolt 16. When the force of the engine oil exceeds the force applied by the locking spring 28, the locking bolt 16 is pushed into the inner sleeve 12, thereby separating the mechanical connection between the inner and outer sleeves 12, 14. In other words, the mechanical connection between the inner and outer sleeves 12, 14 is no longer effective. As a result, a movement by the roller 18 is no longer transmitted to the plunger 8 so that the plunger 8 is idle, i.e. stationary at rest. The corresponding conveying unit is thus idle.

(12) FIG. 1 shows the outer sleeve 14 by way of a cross sectional illustration through a cylindrical wall of the outer sleeve 14. An inner side of the wall of the outer sleeve 14 is partly covered by the inner sleeve 12, the locking bolt 16, and the roller 18, while only a portion of the inner side between the locking bolt 16 and the roller 18 is shown. FIG. 1 also shows the provision of a bore in the wall of the outer sleeve 14 for receiving one end of the locking bolt 16.

(13) While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

(14) What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: