Fuel injection pump equipped with rotary deflector

A fuel injection pump equipped with a rotary deflector having an increased lifetime and reduced maintenance cost required to replace the deflector when it is wasted due to cavitation erosion. The deflector comprises a stationary holder and a tip member which is supported rotatably by the stationary holder so that the tip member is rotated by fuel flow that outbursts from the plunger room through the inlet/spill port and impinges against the tip member when fuel injection ends. This evades concentrated impingement at a specific portion of the tip member and prevents the occurrence of cavitation erosion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel injection pump for diesel engines. Specifically, the present invention relates to a fuel injection pump equipped with deflectors at input/spill ports of a plunger barrel in order to prevent occurrence of cavitations when fuel is spilled through the ports to finish fuel injection by allowing high-pressure fuel spilled from the plunger room through the ports to impinge against the deflectors.

2. Description of the Related Art

In many of jerk fuel injection pumps for diesel engines, deflectors are provided at input/spill ports of the plunger barrel so that fuel spilled from the plunger room at high speed through the ports impinges against the deflectors in order to prevent impingement of the high speed fuel against the casing of the injection pump, since the impingement induces cavitation erosion on the inside surface of the ports and fuel gallery surrounding the ports.

FIG. 5is a sectional view along the center line of a plunger of a jerk fuel injection pump for a diesel engine to which the present invention is applied.

InFIG. 5, a plunger barrel102is fixedly provided in a pump case105. A plunger100is fit in the plunger barrel102to be reciprocated. The plunger100is driven to reciprocate by means of a fuel cam not shown in the drawing via a tappet106and tappet spring107. A plunger room111is formed in the plunger barrel102above the top face of the plunger100. Fuel fed from a fuel gallery104formed between the inner surface of the pump case105and outer surface of the plunger barrel102through the input/spill ports103into the plunger room111is compressed to a high pressure by moving the plunger100in an upward direction. The highly pressurized fuel pushes open a delivery valve108seating on a valve seat110, and the highly pressurized fuel flows through an outlet passage109to a fuel injection valve not shown in the drawing.

Deflectors10are located at the fuel gallery side openings of the inlet/spill ports103. When the spill groove101of the plunger100uncovers the inlet/spill ports103, pressurized fuel in the plunger room outbursts through the ports103and impinges against the deflectors10. Occurrence of cavitation erosion on the surface of the inlet/spill ports103and the fuel gallery104is prevented by the impingement of fuel against the deflectors10.

Fuel injection pumps equipped with deflectors like this are disclosed in Japanese Laid-Open Patent Application No. 2000-179428 (patent literature 1) and Japanese Laid-Open Patent Application No. 9-144627 (patent literature 2).

In the fuel injection pump disclosed in the patent literature 1, the deflector for preventing cavitation erosion is shaped into a hexagonal socket head bolt having a protrusion to be inserted into the inlet/spill port with a plurality of fuel passages drilled to surround the socket part of the bolt to allow fuel that outbursts from the plunger room through the inlet/spill port to flow into the fuel gallery, wherein the deflector is screwed to the plunger barrel and further retained to the plunger barrel by means of a snap ring in order to prevent it from slipping out even when the screw has loosened.

In the fuel injection pump disclosed in the patent literature 2, the deflector is screwed to the pump case to face the inlet/spill port. Porous material is adhered on the end of the deflector facing the port to allow fuel bursting out through the port to impinge against the porous material, thereby alleviating rapid pressure change at the fuel impinging part and preventing occurrence of cavitation erosion.

In these prior art, the deflector is fixed securely to the plunger or pump case.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide an improved deflector for preventing occurrence of cavitation erosion and elongating lifetime of the deflector. The invention proposes a fuel injection pump equipped with a rotary deflector, with which lifetime of the deflector is increased and maintenance cost, which is required to replace the deflector when it is wasted due to cavitation erosion, is decreased.

To attain the object, the present invention proposes a fuel injection pump equipped with rotary deflectors against which spilled fuel that outbursts from a plunger room through inlet/spill ports drilled in a plunger barrel and flows into a fuel gallery when fuel injection ends is allowed to impinge. Each of the rotary deflectors comprises a stationary holder and a rotatable tip member. Further, the stationary holder is fixed to the plunger barrel or a pump case accommodating the plunger barrel. In addition, the rotatable tip member is supported rotatably by the stationary holder. Further, the rotatable tip member has (i) a spilled fuel inlet hole that is drilled in the center of the tip member to open in the inlet/spill ports and (ii) a spilled fuel outlet hole or holes that are drilled radially to open into the fuel gallery and to communicate to the spilled fuel inlet hole.

In the invention, it is preferable that a plurality of the spilled fuel outlet holes are drilled radially in a shape like the spokes of a wheel, and further it is preferable that a plurality of the spilled fuel outlet holes are drilled tangentially to rotation direction of the tip member.

According to the invention, the deflector against which fuel that outbursts through the inlet/spill ports is allowed to impinge is divided into the stationary holder and the rotatable tip member supported rotatably by the stationary holder. The tip member having the spilled fuel inlet hole and spilled fuel outlet hole or holes for allowing the fuel passed through the spilled fuel inlet hole to be flowed out into the fuel gallery, so that the tip member against which fuel that outbursts through the inlet/spill ports is allowed to impinge is rotated by force that the spilled fuel exerts on the tip member. This results in that an impingement of the spilled fuel outbursting through the inlet/spill ports on the tip member at a specific part thereof, as has been the case in conventional deflectors, can be evaded.

Therefore, (i) occurrence of cavitation erosion at the end of the tip member of the deflector caused by repetition of impingement of the high-pressure spilled fuel outbursting from the plunger room through the inlet/spill ports on the end of the tip member is prevented, (ii) lifetime of the deflector is elongated, and (iii) maintenance cost for replacing the deflector is decreased.

Further, by providing a plurality of the spilled fuel outlet holes such that they are drilled tangentially to a rotation direction of the tip member, reaction force is generated by fuel flowing out through the tangential holes to rotate the tip member, so the tip member is positively rotated periodically every time fuel outbursts through the inlet/spill port, and impingement of fuel on the tip member at a specific part of the tip member can be evaded more positively, that is, parts hit by the outbursting fuel are dispersed more positively.

In the invention, it is preferable that the tip member has a flange part to be supported axially by a stationary holder with small side clearances provided between the stationary holder, and radial balance oil passages communicating to the spilled fuel inlet hole and axial balance holes communicating to the radial balance oil passages are drilled in the flange part.

With this construction, a part of spilled fuel introduced into the spilled fuel inlet hole introduced to the side clearances of the flange part of the tip member to lubricate therein, so the tip member can be rotated smoothly without occurrence of sticking or seizure of the flange part of the rotatable tip member, resulting in elongated lifetime of the deflector.

The deflector of the invention can be applied to a so-called solid type deflector. For this type of deflector, the invention proposes a fuel injection pump equipped with rotary deflectors against which spilled fuel that outbursts from a plunger room through inlet/spill ports drilled in a plunger barrel and flows into a fuel gallery when fuel injection ends is allowed to impinge. Each of the rotary deflectors comprises a stationary holder and a rotatable tip member. The stationary holder being fixed to the plunger barrel or a pump case accommodating the plunger barrel. The rotatable tip member is supported rotatably by the stationary holder. Further, the rotatable tip member has (i) a solid part against which fuel that outbursts from the plunger room impinges, (ii) a spilled fuel inlet hole or holes drilled from the outer periphery of the solid part of the tip member intruding into the inlet/spill port toward the center of the solid part of the tip member to communicate to a succeeding center hole, and (iii) a spilled fuel outlet hole or holes that are drilled radially to open into the fuel gallery and to communicate to the center hole in the solid part.

In the invention, it is preferable that a plurality of the spilled fuel outlet holes are drilled radially in a shape like the spokes of a wheel, and further it is preferable that a plurality of the spilled fuel outlet holes are drilled tangentially to rotation direction of the tip member.

According to the invention, fuel that outbursts through the inlet/spill port impinges on the apical portion of the solid part of the rotatable tip member and enters the spilled fuel inlet hole or holes. As a result, the tip member can be rotated by the spilled fuel flow. Therefore, portions where the spilled fuel impinges upon are dispersed and repeated fuel impingement on a specific portion can be evaded.

Further, by providing a plurality of the spilled fuel outlet holes such that they are drilled tangentially to rotation direction of the tip member, reaction force is generated by fuel flowing out through the tangential holes to rotate the tip member, so the tip member is positively rotated periodically every time fuel outbursts through the inlet/spill port, and impingement of fuel against the tip member at a specific part of the tip member can be evaded more positively, that is, parts hit by the outbursting fuel are dispersed more positively.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will now be detailed with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, relative positions and so forth of the constituent parts in the embodiments shall be interpreted as illustrative only not as limitative of the scope of the present invention.

The First Embodiment

FIG. 1Ais a sectional view of the deflector in a jerk fuel injection pump of a first embodiment for a diesel engine (corresponding to part Y inFIG. 5), andFIG. 1Bis an enlarged detail of part Z inFIG. 1A.

Referring toFIG. 1, a plunger barrel102is fixedly provided in a pump case105. A plunger100is fit in the plunger barrel102to be reciprocated. The plunger100is driven to reciprocate by means of a fuel cam not shown in the drawing via a tappet106and tappet spring107.

A plunger room111is formed in the plunger barrel102above the top face of the plunger100. Fuel fed from a fuel gallery104formed between the inner surface of the pump case105and outer surface of the plunger barrel102through the input/spill ports into the plunger room111is compressed to a high pressure by moving up of the plunger100and supplied to an injection valve not shown in the drawing.

When a spill groove101of the plunger100uncovers the inlet/spill ports103, pressurized fuel in the plunger room111flows through the ports103into the fuel gallery104.

A deflector10is located at each of the inlet/spill port103so that highly pressurized fuel that outbursts through the inlet/spill port103when the spill groove101of the plunger100uncovers the port103while moving up impinges against the deflector10. Occurrence of cavitation erosion on the surface of the inlet/spill ports103and the fuel gallery104is prevented by the impingement of fuel against the deflectors10.

The deflector10comprises a stationary holder comprising case member2screwed to the pump case105and a bolt member3screwed into the case member2, and a tip member1held rotatably by the case member2.

The tip member1has a tapered tip part1d, a cylindrical part1c, and a flange part1a. The cylindrical part1cand flange part1aof the tip member1is received in the case member2so that the tip member1is rotatable relative to the case member.

The case member2is screwed into the pump case105via a gasket29. The bolt member3is screwed into the case member2so that the end face thereof supports axially the end face of the flange part1aof the tip member1. Reference numeral11is an ‘O’ ring for sealing the outer circumference of the bolt member3and inner circumference of the case member2.

The deflector10is fixed to the pump case such that the tapered tip part1dof the tip member1intrudes into the port103.

The flange part1aof the tip member1is held between the end face of the bolt member3and the shoulder face inside the case member2with small gaps9,9retained in axial direction of the deflector10, and radial balance oil passages7,7and axial balance oil passage8,8are provided to the flange part1ato introduce a part of fuel entered a central hollow6through a spilled fuel inlet opening5mentioned later of the tip member1to the gaps9,9, as shown inFIG. 1Bso that the small gaps9,9are always filled with fuel.

With the construction, a part of fuel spilled fuel is introduced into the small gaps9,9, the tip member1can rotate in the case member smoothly in a state sufficiently lubricated by fuel oil, so occurrence of sticking or seizure of the tip member1is prevented, resulting in elongated lifetime of the deflector10.

The tip member1has a spilled fuel inlet opening5and a central hollow6communicating to the inlet opening5, and a plurality of spilled fuel outlet holes4(four holes in this example) are drilled radially in the cylindrical part1cof the tip member1to open toward the fuel gallery104.

FIG. 3is a first example of the spilled fuel outlet holes4shown in a section along line A-A inFIG. 1A. In the example, four spilled fuel outlet holes4are drilled radially with the center axes thereof passing the center10aof the central hollow6of the tip member1.

FIG. 2is a second example of the spilled fuel outlet holes4shown in a section along line A-A inFIG. 1A. In the example, four spilled fuel outlet holes4are drilled tangential to the circumference of the central hollow6of the tip member1. In this case, reaction force is generated by fuel flowing out through the spilled outlet holes4to rotate the tip member1, the tip member1is positively rotated periodically every time fuel outbursts through the inlet/spill ports, so impingement of fuel against the tip member at a specific part of the tip member can be evaded more positively, that is, parts hit by the outbursting fuel are dispersed more positively.

InFIGS. 1 to 3, reference numeral10ais the center of the deflector10.

According to the first embodiment, the deflector10against which fuel that outbursts through the inlet/spill ports103is allowed to impinge is divided into a stationary holder including the case member2and bolt member3and the rotatable tip member1supported rotatably by the stationary holder, the tip member having the spilled fuel inlet hole5and the plurality of spilled fuel outlet holes4for allowing the fuel passed through the spilled fuel inlet hole5to be flowed out into the fuel gallery104, so the tip member1against which fuel that outbursts through the inlet/spill ports103is allowed to impinge is rotated by force that the spilled fuel exerts on the tip member1.

This results in the impingement of the spilled fuel outbursting through the inlet/spill ports103against the tip member1at a specific part thereof, as has been the case in conventional deflectors, being evaded.

Therefore, (i) occurrence of cavitation erosion at the end of the tip member1of the deflector10caused by repetition of impingement of the high-pressure spilled fuel outbursting through the inlet/spill ports103on the end of the tip member1is prevented, (ii) lifetime of the deflector10is elongated, and (iii) maintenance cost for replacing the deflector10is decreased.

The Second Embodiment

FIG. 4Ais a sectional view of the deflector in a jerk fuel injection pump of a second embodiment for a diesel engine (corresponding to part Y inFIG. 5), andFIG. 4Bis a section B-B inFIG. 4A.

The second embodiment is a case the invention is applied to a so-called solid type deflector. In the drawing, the deflector10comprises a stationary holder which includes a case member2and a bolt member3screwed into the pump case, and a tip member1which is supported rotatably by the stationary members and of which an end intrudes into the inlet/spill port103. The tip member1has a solid end part1bintruding into the port103. A plurality of spilled fuel inlet holes21, a center hole23, and a central hollow6are formed in the tip member1. The spilled fuel inlet holes21are drilled from the outer periphery of the solid part1btoward the center of the solid part of the tip member1to be communicated with the center hole23. A plurality of spilled fuel outlet holes22are drilled radially in the cylindrical part of the tip member1to communicate the central hollow with the fuel gallery104. The flange part1aof the tip member is formed the same as that of the tip member of the first embodiment.

As shown inFIG. 4B, four spilled fuel inlet holes21and four spilled fuel outlet holes22are provided in this example such that they deviate by 45° from each other in circumferential direction.

The spilled fuel outlet holes22may be drilled tangential to the circumference of the central hollow6. In this case, reaction force is generated by fuel flowing out through the spilled fuel outlet holes22to rotate the tip member1, the tip member is positively rotated periodically every time fuel outbursts through the inlet/spill ports, so impingement of fuel against the tip member at a specific part of the tip member can be evaded more positively, that is, parts hit by the outbursting fuel are dispersed more positively.

Construction other than that mentioned above is the same as that of the first embodiment, and constituent members the same as those of the first embodiment are denoted by the same reference numerals.

With the deflector of the second embodiment, fuel that outbursts from the inlet/spill port103impinges on the solid end part1bof the tip member1and then part of spilled fuel enters the spilled fuel inlet holes21, and the tip member1is rotated by the impingement of fuel. Therefore, impinging portions of the fuel outbursting through the inlet/spill port103on the solid part1bof the tip member1are dispersed and concentrated impingement on a specific portion of the solid part1bcan be evaded.

According to the invention, the deflector is divided into a stationary holder and a rotatable tip member supported rotatably by the stationary holder, fuel that outbursts through the inlet/spill port impinges against the tip member and exerts force to rotate the tip member, so concentrated impingement of the outbursting fuel on a specific portion of the tip member is evaded, resulting in that occurrence of cavitation erosion on the impinging part of the tip member due to repeated impingement of the outbursting fuel is prevented. Therefore, lifetime of the deflector is elongated and maintenance cost for replacing the deflector can be decreased.

Further, by constructing the rotary tip member such that a plurality of spilled fuel outlet holes for allowing spilled fuel entered the tip member to flow out from the tip member are drilled tangential to the circumference of the central hollow of the tip member, reaction force is generated by fuel flowing out through the tangential holes to rotate the tip member, so the tip member is positively rotated periodically every time fuel outbursts through the inlet/spill ports and part of the fuel enters the tip member, parts on the tip member hit by the outbursting fuel are dispersed more positively.