JP2003003928A - Fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection pump having improved reliability by preventing the occurrence of fretting wear. SOLUTION: A predetermined clearance is provided in a mating face between a bearing cover 60 and a housing body 11. If the pressure and forcible feed of a fuel by a plunger 20 gives tensile force to the housing body 11 via cylinder heads 12, 13 in an area near a fitting hole 11a where a bolt cannot be arranged for fixing a bearing cover 60 to the housing body 11, no slight, repetitive and relative slide involving friction force is caused between the bearing cover 60 and the housing body 11. Thus, the occurrence of the fretting wear on the mating face between the bearing cover 60 and the housing body 11 is prevented and the looseness and breakage of the bolt, the seizure of the plunger 20 and the leakage of the fuel are prevented, resulting in improved reliability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an internal combustion engine (hereinafter,
The "internal combustion engine" is called an engine. ) For fuel injection pump.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection pump for an engine, a plurality of plungers are arranged radially around a cam,
There is known a so-called star pump that pressurizes fuel sucked into a fuel pressurizing chamber formed for each plunger. In the star pump, the fuel pressure feed passages for delivering the high-pressure fuel pressurized in the fuel pressurizing chamber are merged directly into the pump housing, and the fuel is fed from the merged fuel pressure feed passages to the common rail. Is common.

[0003]

By the way, in the pressure-accumulation type fuel injection pump, the drive shaft can be rotated due to the layout restriction in which the fitting hole of the element for supporting the plunger to reciprocate is formed in the pump housing. There was an area in which bolts or the like for fixing the support member supporting to the pump housing to the pump housing could not be arranged. for that reason,
In the region where the bolt cannot be arranged, the tightening force of the bolt does not act, and the surface pressure of the mating surface between the support member and the pump housing decreases. Further, since the pump housing holds the element forming the fuel pressurizing chamber, when the plunger moves up to pressurize and pump the fuel,
The pump housing receives a pulling force via the element. Therefore, there has been a problem that a small amount of repeated relative sliding accompanied by a frictional force occurs at the low surface pressure portion between the support member and the pump housing, and so-called fretting wear occurs.

When fretting wear occurs, the generated wear debris is not easily discharged and has a great influence on the wear and frictional behavior of the mating surface between the support member and the pump housing, resulting in significant local friction and large frictional force. Cause Therefore, there is a problem that the bolt axial force decreases at the fretting action position, and there is a risk that the bolt may loosen or break, the plunger may seize, and fuel may leak.

The above problem is that the pump housing and the supporting member are made large in size to eliminate the region where the bolt cannot be arranged, and the tightening force by the bolt is made uniform so that the mating surface between the supporting member and the pump housing is made uniform. It is possible to solve the problem by suppressing the decrease of the surface pressure. However, when the pump housing and the supporting member are made large in size, the space occupied by the fuel injection pump increases, making it difficult to secure a mounting space. In addition, the weight of the fuel injection pump increases and fuel consumption is reduced. There was a problem that it would be difficult to meet the demand.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel injection pump which prevents the occurrence of fretting wear and improves reliability. Another object of the present invention is to eliminate the low surface pressure portion,
It is to provide a fuel injection pump that prevents relative slippage between members. Still another object of the present invention is to provide a fuel injection pump which is easy to manufacture while being downsized and lightweight.

[0007]

According to the fuel injection pump of the first aspect of the present invention, the mating surface between the housing body and the support member fixed to the housing body and rotatably supporting the drive shaft is provided. , Contact escape means having a predetermined clearance is provided. Therefore, by forming the fitting hole of the element in the housing body, in the region where the bolts or the like for fixing the support member to the housing body cannot be arranged, the housing body is pressurized and pumped by the movable member. Even if the element receives a tensile force through the element, by providing a predetermined clearance on the mating surface between the housing body and the support member, the low surface pressure part where the surface pressure due to the tightening force of the bolt etc. does not reach the predetermined surface pressure is eliminated. As a result, it is possible to prevent a slight repetitive relative slip between the housing body and the support member due to frictional force. Therefore, fretting wear is prevented from occurring on the mating surface of the housing main body and the support member, and loosening and breakage of bolts and the like, seizure of the movable member, and fuel leakage are prevented. Reliability can be improved.

Furthermore, the physiques of the housing main body and the supporting member are reduced in size, the space occupied by the fuel injection pump is reduced, and it is easy to secure a mounting space, and the members of the housing main body and the supporting member are relatively hard. By forming a metal such as aluminum that is low and lightweight, it becomes easy to reduce the weight of the fuel injection pump and meet the demand for realizing the reduction of fuel consumption.

According to the fuel injection pump of the second aspect of the present invention, the fretting wear is easily generated with a relatively simple structure in which the mating surface on one side or both sides of the housing body and the supporting member is provided with a recess. Can be prevented. Therefore, it is possible to easily reduce the size and weight, facilitate the manufacturing, and reduce the manufacturing cost.

According to the fuel injection pump of the third aspect of the present invention, since the projection portion that can come into contact with the mating surface on the housing body or the supporting member side is provided in the recessed portion,
When the movable member pressurizes and pressure-feeds the fuel, the protrusion is used as a fulcrum to prevent the drive shaft from rattling, thereby preventing the support member from being deformed. Therefore, it is possible to reliably prevent the seizure of the movable member and the occurrence of fuel leakage. In this case, pressurization of fuel by the movable member
It is possible that the protrusions will wear during pressure feeding,
The wear debris generated at that time is easily discharged from the recess to the outside, and the wear debris does not affect the mating surface between the housing body and the support member, which does not adversely affect the occurrence of fretting wear. Do not give.

According to the fuel injection pump of the fourth aspect of the present invention, the plate member which can be brought into close contact with the housing body and the supporting member is provided on the mating surface between the housing body and the supporting member, and thus the flexing can be easily performed. It is possible to prevent the occurrence of coating wear. Therefore, it is possible to easily reduce the size and weight, facilitate the manufacturing, and reduce the manufacturing cost.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of examples showing an embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 4 show a fuel injection pump for a diesel engine according to a first embodiment of the present invention.

As shown in FIG. 4, the pump housing of the fuel injection pump 10 has a housing body 11 and cylinder heads 12 and 13. The housing body 11 is made of aluminum. The cylinder heads 12 and 13 are made of iron and support a plunger 20 as a movable member so as to be reciprocally movable. A fuel pressurizing chamber 30 is formed by the inner peripheral surfaces of the cylinder heads 12 and 13, the end surface of the check valve 23, and the end surface of the plunger 20. The cylinder heads 12 and 13 as elements are fitted into a fitting hole 11a formed in the housing body 11, and are held on the inner wall of the fitting hole 11a as shown in FIG.
It is fixed to the housing body 11 by tightening the screws. In the first embodiment, the cylinder heads 12 and 13 are formed in substantially the same shape, but the forming positions of screw holes, fuel passages, etc. are different. On the other hand, it is possible to form the cylinder heads 12 and 13 in exactly the same shape by forming the screw holes and the fuel passages at the same position.

The drive shaft 14 is rotatably supported by a bearing cover 60 as a support member via a journal 15. As shown in FIG. 3, the bearing cover 60
Is fixed to the housing body 11 by tightening a bolt 70 in a region other than the vicinity of the fitting holes 11 a of the cylinder heads 12 and 13. Bearing cover 6
An oil seal 16 seals between 0 and the drive shaft 14. The cam 17 having a circular cross section is eccentrically formed with respect to the drive shaft 14 and is integrally formed. 18 across the drive shaft 14
Each plunger 20 is arranged on the opposite side of 0 °. A bush 19 is interposed between the shoe 18 and the cam 17 so as to be slidable with the shoe 18 and the cam 17. Plunger 2
0 and the outer peripheral surface of the shoe 18 and the plunger head 2
The end surface of 0a is formed in a flat shape and is in contact with each other.

The plunger 20 is reciprocally driven by the cam 17 via the shoe 18 as the drive shaft 14 rotates.
The fuel pressurizing chamber 30 passes from the fuel inflow passage 31 through the check valve 23.
Pressurize the fuel drawn into. The check valve 23 is a valve member 23.
With a, it prevents the fuel from flowing backward from the fuel pressurizing chamber 30 to the fuel inflow passage 31.

The spring 21 urges the plunger 20 toward the shoe 18. Shoe 18 and plunger 2
Since each contact surface of 0 is formed flat,
The surface pressure between the shoe 18 and the plunger 20 decreases. Further, with the rotation of the cam 17, the shoe 18 revolves without sliding while sliding on the cam 17.

As shown in FIG. 4, the fuel discharge passage 32 is linearly formed in the cylinder head 12, and has a communication port 32a for communicating with the fuel pressurizing chamber 30. On the downstream side of the fuel discharge passage 32 formed in the cylinder head 12, a long hole-shaped fuel chamber 33 having a larger passage area than the fuel discharge passage 32 is formed, and a check valve 44 is accommodated in the fuel chamber 33. There is. A storage hole 34 having a larger passage area than the fuel chamber 33 is formed on the fuel downstream side of the fuel chamber 33. Accommodation hole 34
Is opened on the outer peripheral wall of the cylinder head 12 and is located at the fuel outlet 34a
Is formed. The fuel discharge passage 32, the fuel chamber 33, and the accommodation hole 34 form a fuel pressure feeding passage. The connecting member 41 for connecting the fuel pipe is housed in the housing hole 34 by screwing or the like. A fuel passage 41 a is formed inside the connection member 41, and the fuel passage 41 a communicates with the fuel chamber 33. The fuel passage 41a is formed substantially on the same straight line as the fuel discharge passage 32.

The check valve 44 disposed on the fuel downstream side of the fuel discharge passage 32 of the cylinder head 12 includes a ball-shaped valve member 45 and a spring 47 for urging the valve member 45 toward the valve closing side. Have The check valve 44 prevents the fuel from flowing backward from the fuel chamber 33 on the fuel downstream side of the check valve 44 to the fuel pressurizing chamber 30 via the fuel discharge passage 32. The connecting member 41 is connected by a fuel pipe to a common rail as a storage pressure member (not shown), and the fuel pressurized by the fuel injection pump 10 is supplied from the connecting member 41 to the common rail. A fuel discharge passage (not shown) is formed in the cylinder head 13 similarly to the cylinder head 12, and a fuel discharge passage (not shown) is connected to the fuel chamber 33 via a fuel pipe (not shown) on the fuel downstream side of the fuel discharge passage. A stop valve is provided.

The inner gear type feed pump 50 pressurizes the fuel sucked from a fuel tank (not shown) through a fuel inlet (not shown) and sends it to a fuel passage (not shown). When the fuel pressure in the feed pump 50 becomes equal to or higher than a predetermined pressure, a regulation valve (not shown) opens and excess fuel is returned to the fuel tank. Further, the housing body 11 is provided with a metering solenoid valve (not shown) for metering the amount of fuel sucked into the fuel pressurizing chamber 30 from the fuel inflow passage 31 through the check valve 23 in accordance with the engine operating state. There is.

Next, the mating surface between the bearing cover 60 and the housing body 11 will be described in detail with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the bearing cover 60 is a generally cylindrical aluminum member, and has a substantially arc-shaped contact portion 62 on the outer peripheral end surface on the housing body 11 side, that is, a mating surface with the housing body 11. Two recesses 61 are provided in each. Adhesion part 62
Has a plurality of bolt holes 64, and a plurality of bolt holes 6
4, the bolt 70 shown in FIG. 3 is screwed. The bearing cover 60 is attached to the housing body 1 by tightening the bolt 70.
1 is fixed to the housing main body 11
Adhere to the mating surface on the side. At this time, the recess 61 is located near the fitting holes 11 a of the cylinder heads 12 and 13. A stepped portion 63 is formed at a boundary portion between the close contact portion 62 and the recessed portion 61 where a predetermined surface pressure is generated by screwing the bolt 70, and the stepped portion 63 has a height of 0.
Since it is about 2 mm to 1.0 mm, the recess 61 does not come into contact with the mating surface on the housing body 11 side. That is, a predetermined clearance is provided on the mating surface between the bearing cover 60 and the housing body 11. Here, the height of the stepped portion 63 may be any dimension as long as the recessed portion 61 does not contact the mating surface of the housing body 11. The recessed portion 61 and the stepped portion 63 constitute contact escape means.

Next, the operation of the fuel injection pump 10 will be described. The cam 17 rotates as the drive shaft 14 rotates,
With the rotation of the cam 17, the shoe 18 revolves without rotating. With the revolution of the shoe 18, the planar contact surfaces of the shoe 18 and the plunger 20 slide with each other, whereby the plunger 20 reciprocates.

When the plunger 20 at the top dead center descends as the shoe 18 revolves, the fuel discharged from the feed pump 50 is adjusted by the control of the metering solenoid valve, and the adjusted fuel is reversed from the fuel inflow passage 31. Fuel flows into the fuel pressurizing chamber 30 through the stop valve 23. When the plunger 20 that has reached the bottom dead center rises toward the top dead center again, the check valve 23 closes and the fuel pressure in the fuel pressurizing chamber 30 increases. When the fuel pressure in the fuel pressurizing chamber 30 rises above the fuel pressure in the fuel passage 41a, the check valve 44 opens.

The fuel pressurized in the fuel pressurizing chamber 30 on the cylinder head 12 side is delivered from the fuel discharge passage 32, the check valve 44, and the fuel chamber 33 to the fuel passage 41a. The fuel pressurized in the fuel pressurizing chamber 30 on the cylinder head 13 side flows into the fuel chamber 33 via a fuel pipe (not shown). The fuel pressurized in both fuel pressurizing chambers 30 merges in the fuel chamber 33,
It is supplied to the common rail from the fuel passage 41a. The common rail accumulates the fuel having a pressure fluctuation supplied from the fuel injection pump 10 and holds it at a constant pressure. High-pressure fuel is supplied to the injector (not shown) from the common rail.

Next, a bearing cover of a comparative example will be described with reference to FIGS. 7 and 8. The bearing cover 160 shown in FIG. 8 is different from the bearing cover 60 of the first embodiment shown in FIG. 2 in the structure of the mating surface with the housing body 11, and the other structures are the same as those in the first embodiment. The same reference numerals are given to substantially the same components.

As shown in FIGS. 7 and 8, the bearing cover 160 is provided with a substantially annular contact portion 162 on the mating surface with the housing body 11. Contact part 16
2 has a plurality of bolt holes 164, and the bolts 70 of the first embodiment shown in FIG. 3 are screwed into the plurality of bolt holes 164. By tightening the bolt 70, the bearing cover 16
When 0 is fixed to the housing body 11, the contact portion 16
2 closely contacts the mating surface on the housing body 11 side. At this time, since the bolt hole 164 cannot be arranged in the area near the fitting holes 11a of the cylinder heads 12 and 13, the surface pressure due to the tightening force of the bolt 70 does not reach the predetermined surface pressure in this area, Bearing cover 160
The surface pressure of the mating surface between the housing and the housing body 11 decreases.
Further, since the housing body 11 holds the cylinder heads 12 and 13 forming the fuel pressurizing chamber 30, when the plunger 20 moves up to pressurize and pump the fuel, the housing body 11 moves the cylinder heads 12 and 13 to each other. Receive a pulling force through. Therefore, the bearing cover 1
In the low surface pressure portion between the housing 60 and the housing body 11, a slight repetitive relative slippage accompanied by a frictional force may occur and fretting wear may occur.

When fretting wear occurs, the generated wear powder is not easily discharged from the mating surface between the bearing cover 160 and the housing body 11, which has a great influence on the wear and friction behavior of the bearing cover 160 and the housing body 11. Exerts a significant local friction and a large frictional force. Therefore, at the fretting action position, which is a region near the fitting holes 11a of the cylinder heads 12 and 13, the bolt axial force is reduced, the bolt 70 is loosened or broken, the plunger 20 is seized, and fuel leaks. There is a problem that there is a risk of doing it.

On the other hand, in the first embodiment, the fitting holes 11a of the cylinder heads 12 and 13 are formed in the housing main body 1.
In the region in which the bolt 70 for fixing the bearing cover 60 to the housing body 11 cannot be arranged, the housing body 11 presses and pumps the fuel by the plunger 20 to cause the housing body 11 to move the cylinder heads 12 and 13 to each other. By providing a predetermined clearance on the mating surface between the bearing cover 60 and the housing body 11 even if a pulling force is applied through, a low surface pressure portion where the surface pressure due to the tightening force of the bolt 70 does not reach the predetermined surface pressure is eliminated, It is possible to prevent a slight repetitive relative sliding between the bearing cover 60 and the housing body 11 due to frictional force. Therefore, it is possible to prevent fretting wear from occurring on the mating surface between the bearing cover 60 and the housing main body 11, and to prevent loosening or breakage of the bolt 70, seizure of the plunger 20, or fuel leakage. It can prevent and improve reliability.

Further, in the first embodiment, the housing body 11 and the bearing cover 60 are made small in size, the space occupied by the fuel injection pump 10 is reduced, and the mounting space can be easily secured. 11 and the members of the bearing cover 60 are made of a metal such as aluminum which has a relatively low hardness and is lightweight,
It becomes easy to meet the demand for reducing the weight of the fuel injection pump 10 and reducing fuel consumption.

Furthermore, in the first embodiment, the occurrence of fretting wear can be easily prevented with a relatively simple structure in which the recess 61 is provided on the mating surface on the bearing cover 60 side. Therefore, it is possible to easily reduce the size and weight, facilitate the manufacturing, and reduce the manufacturing cost.

In the first embodiment described above, the concave portion 61 is provided on the mating surface on the bearing cover 60 side, but a concave portion may be provided on the mating surface on the housing body 11 side, or the bearing cover 60 and the housing. You may provide a recessed part in the mating surface on both sides with the main body 11.

(Second Embodiment) A second embodiment is shown in FIG.
The same components as those in the first embodiment shown in FIG. 2 are designated by the same reference numerals. As shown in FIG. 5, the bearing cover 80 of the second embodiment is provided with the protrusion 81 in the recess 61. The protrusion 81 is provided so that an imaginary line connecting the protrusions 81 passes through substantially the center of the drive shaft 14, that is, at a position overlapping the plunger, and the height thereof is equal to the height of the step 63, or It is slightly smaller than the height of the step portion 63. The protrusion 81 can contact the mating surface on the housing body side.

Also in the second embodiment, the same effect as that of the first embodiment shown in FIG. 2 can be obtained. Further, since the projection 81 that can come into contact with the mating surface on the housing body side is provided in the recess 61, the projection 81 serves as a fulcrum when the plunger pressurizes and pumps the fuel.
The backlash is prevented from occurring and the bearing cover 80 is prevented from being deformed. Therefore, it is possible to reliably prevent the seizure of the plunger and the occurrence of fuel leakage. In the second embodiment, it is conceivable that the protrusion 81 may be worn when the plunger pressurizes and pumps the fuel, but the abrasion powder generated at that time is easily discharged from the recess 61 to the outside. The abrasion powder does not affect the mating surface between the bearing cover 60 and the housing body, and does not adversely affect the prevention of fretting abrasion.

(Third Embodiment) FIG. 6 shows a third embodiment.
The plate member 90 of the third embodiment shown in FIG. 6 is provided on the mating surface between the bearing cover 160 of the comparative example shown in FIGS. 7 and 8 and the housing body 11. The plate member 90 is a pair of arc-shaped members, and includes a plurality of bolt holes 9
Have four. The bolt hole 94 is the bearing cover 1
It is formed at a position overlapping the bolt holes 164 of 60.
When the plate member 90 is fixed to the mating surface between the bearing cover 160 and the housing body 11 by tightening the bolts, one contact portion 92 of the plate member 90 closely contacts the mating surface on the bearing cover 160 side and the other closely contacts. The portion 96 comes into close contact with the mating surface on the housing body 11 side. At this time, a predetermined clearance is formed on the mating surface between the bearing cover 160 and the housing body 11, and the predetermined clearance is located near the fitting hole of the cylinder head.

Also in the third embodiment, the same effect as that of the first embodiment shown in FIG. 2 can be obtained. Further, the occurrence of fretting wear can be easily prevented with a relatively simple configuration in which the plate member 90 is provided on the mating surface between the bearing cover 160 and the housing body 11. Therefore, it is possible to easily reduce the size and weight, and
Manufacturing is facilitated and manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a fuel injection pump according to a first embodiment of the present invention.

FIG. 2 is a front view showing a mating surface on a bearing cover side of the fuel injection pump according to the first embodiment of the present invention.

FIG. 3 is a partially cutaway front view showing a fuel injection pump according to a first embodiment of the present invention.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a front view showing a mating surface on a bearing cover side of a fuel injection pump according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a plate member of a fuel injection pump according to a third embodiment of the present invention.

FIG. 7 is a sectional view showing a main part of a fuel injection pump according to a comparative example.

FIG. 8 is a front view showing a mating surface on a bearing cover side of a fuel injection pump according to a comparative example.

[Explanation of symbols]

10 Fuel injection pump 11 Housing body (pump housing) 12, 13 Cylinder head (element) 14 Drive shaft 17 cam 20 Plunger (movable member) 30 Fuel pressurizing chamber 31 Fuel inflow passage 32 Fuel discharge passage (fuel pressure passage) 33 Fuel chamber (fuel pressure passage) 60, 80 Bearing cover (support member) 61 Recessed portion (contact escape means) 62 Close contact part 63 Step (contact escape means) 70 volts 81 Projection 90 Plate member

Claims (4)

[Claims] 1. A drive shaft, a cam that rotates together with the drive shaft, and a cam that is disposed on the outer periphery of the cam and reciprocates as the cam rotates to pressurize the fuel sucked into the fuel pressurizing chamber. A movable member for delivering the fuel to the fuel pressure feed passage, an element having the fuel pressure feed passage and supporting the movable member so as to be capable of reciprocating, and a fitting hole into which the element can fit, A housing main body that holds the element by an inner wall, a support member that is fixed to the housing main body and rotatably supports the drive shaft, and is provided on a mating surface between the housing main body and the support member, and has a predetermined clearance. A fuel injection pump comprising: a contact escaping means. 2. The fuel injection pump according to claim 1, wherein the contact escape means has a recess provided in the mating surface on one side or both sides of the housing body and the support member. 3. The fuel injection according to claim 2, wherein the contact escape means has a protrusion provided in the recess and capable of contacting the mating surface on the housing body or the support member side. pump. 4. The fuel injection pump according to claim 1, wherein the contact escape means has a plate member which is provided on the mating surface and which can be brought into close contact with the housing body and the support member.