JP4203708B2 - Fuel injection pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection pump for an internal combustion engine (hereinafter, “internal combustion engine” is referred to as an engine).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a fuel injection pump for an engine, a so-called star pump is known in which a plurality of plungers are arranged radially on the outer periphery of a cam and the fuel sucked into a fuel pressurizing chamber formed for each plunger is pressurized. ing. In the star pump, the fuel pumping passage for sending the high-pressure fuel pressurized in the fuel pressurizing chamber is directly merged into one in the pump housing, and the fuel is fed from the merged fuel pumping passage to the common rail. Is common.
[0003]
[Problems to be solved by the invention]
By the way, in the pressure accumulation type fuel injection pump, a support member that rotatably supports the drive shaft is provided in the pump housing due to a layout restriction in which a fitting hole of an element that supports the plunger so as to be reciprocally movable is formed in the pump housing. There was an area where bolts or the like for fixing could not be arranged. For this reason, in the region where the bolt cannot be disposed, the bolt tightening force does not reach and the surface pressure of the mating surface between the support member and the pump housing decreases. Further, since the pump housing holds an element that forms the fuel pressurizing chamber, when the plunger is raised and the fuel is pressurized and pumped, the pump housing receives a tensile force through the element. For this reason, there has been a problem that so-called fretting wear occurs due to a slight repeated relative slip accompanied by a frictional force at a low surface pressure portion between the support member and the pump housing.
[0004]
When fretting wear occurs, the generated wear powder is not easily discharged, greatly affecting the wear and frictional behavior of the mating surfaces of the support member and the pump housing, resulting in significant local friction and large frictional forces. Therefore, at the fretting operation position, there is a problem that the bolt axial force is reduced, the bolt may be loosened or broken, the plunger may be seized, or fuel leakage may occur.
[0005]
The above problem is that the pump housing and the support member are made large in size, the area where the bolt cannot be arranged is eliminated, the tightening force by the bolt is made uniform, and the surface pressure of the mating surface between the support member and the pump housing is increased. It is possible to solve the problem by suppressing the decrease. However, if the size of the pump housing and the support member is increased, the occupied space of the fuel injection pump increases, making it difficult to secure the mounting space, and the weight of the fuel injection pump is increased, thereby reducing fuel consumption. Therefore, there is a problem that it becomes difficult to meet the demand.
[0006]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel injection pump that prevents occurrence of fretting wear and improves reliability.
Another object of the present invention is to provide a fuel injection pump that eliminates a low surface pressure portion and prevents relative slip between members.
Still another object of the present invention is to provide a fuel injection pump that can be reduced in size and weight and can be easily manufactured.
[0007]
[Means for Solving the Problems]
According to the fuel injection pump of the first aspect of the present invention, the fuel injection pump is disposed on the outer periphery of the cam that rotates together with the drive shaft, and moves back and forth in the vertical direction with respect to the drive shaft as the cam rotates. the sucked fuel is pressurized, a movable member for delivering the fuel pumping passage, and the housing body, against the housing body is fixed in contact with the end portion in the axial direction of the drive shaft, rotatably supporting the drive shaft Contact escape means having a predetermined clearance is provided on a mating surface perpendicular to the axial direction of the drive shaft with the support member. For this reason, by forming the fitting hole of the element in the housing main body, the housing main body is pressurized and pumped by the movable member in a region where a bolt or the like for fixing the support member to the housing main body cannot be arranged. Even if it receives a pulling 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 bolts etc. does not reach the predetermined surface pressure is eliminated. Thus, it is possible to prevent a minute and repeated relative slip accompanied by a frictional force between the housing body and the support member. Therefore, fretting wear is prevented from occurring on the mating surface of the housing body and the support member, and it is possible to prevent loosening of bolts, breakage, seizure of the movable member, and fuel leakage. Reliability.
[0008]
Further, the housing body and the support member can be made smaller in size, the space occupied by the fuel injection pump can be reduced, and the mounting space can be secured easily. By forming it with a metal such as aluminum, it becomes easy to reduce the weight of the fuel injection pump and meet the demands for reducing fuel consumption.
[0009]
According to the fuel injection pump of the second aspect of the present invention, the occurrence of fretting wear can be easily prevented with a relatively simple configuration in which a recess is provided on the mating surface on one or both sides of the housing body and the support member. be able to. Therefore, it is possible to easily reduce the size and weight, facilitate manufacturing, and reduce manufacturing costs.
[0010]
According to the fuel injection pump of the third aspect of the present invention, since the recess is provided in the recess so as to be able to contact the mating surface on the housing body or the support member side, when the fuel is pressurized and pumped by the movable member The protruding portion serves as a fulcrum to prevent the drive shaft from rattling and the support member from being deformed. Therefore, the seizure of the movable member and the occurrence of fuel leakage can be reliably prevented. In this case, it is conceivable that the protrusions are worn during the pressurization / pumping of the fuel by the movable member. However, the wear powder generated at that time is easily discharged to the outside from the recess, and the wear powder is removed from the housing. It does not affect the mating surface between the main body and the support member, and does not adversely affect the occurrence of fretting wear.
[0011]
According to the fuel injection pump of the fourth aspect of the present invention, the fretting wear can be easily made with a relatively simple structure in which the plate member capable of being in close contact with the housing body and the support member is provided on the mating surface of the housing body and the support member. Occurrence can be prevented. Therefore, it is possible to easily reduce the size and weight, facilitate manufacturing, and reduce manufacturing costs.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plurality of examples showing embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
1 to 4 show a fuel injection pump for a diesel engine according to a first embodiment of the present invention.
[0013]
As shown in FIG. 4, the pump housing of the fuel injection pump 10 includes 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 fitting holes 11a formed in the housing main body 11, held on the inner wall of the fitting holes 11a, as shown in FIG. It is fixed to the main body 11. In the first embodiment, the cylinder heads 12 and 13 are formed in substantially the same shape, but the formation positions of screw holes and fuel passages are different. On the other hand, it is also 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 positions.
[0014]
The drive shaft 14 is rotatably supported by a bearing cover 60 as a support member via the journal 15. As shown in FIG. 3, the bearing cover 60 is fixed to the housing main body 11 by tightening bolts 70 in a region excluding the vicinity of the fitting holes 11 a of the cylinder heads 12 and 13. The bearing cover 60 and the drive shaft 14 are sealed with an oil seal 16. The cam 17 having a circular cross section is integrally formed eccentrically with respect to the drive shaft 14. Plungers 20 are arranged on the opposite side of 180 ° across the drive shaft 14. 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. The outer peripheral surface of the shoe 18 facing the plunger 20 and the end surface of the plunger head 20a are formed in a flat shape and are in contact with each other.
[0015]
The plunger 20 is reciprocally driven by the cam 17 through the shoe 18 as the drive shaft 14 rotates, and pressurizes the fuel sucked into the fuel pressurizing chamber 30 from the fuel inflow passage 31 through the check valve 23. The check valve 23 has a valve member 23 a and prevents the fuel from flowing backward from the fuel pressurizing chamber 30 to the fuel inflow passage 31.
[0016]
The spring 21 urges the plunger 20 toward the shoe 18 side. Since the contact surfaces of the shoe 18 and the plunger 20 are formed in a planar shape, the surface pressure between the shoe 18 and the plunger 20 decreases. Further, as the cam 17 rotates, the shoe 18 revolves without rotating while sliding with the cam 17.
[0017]
As shown in FIG. 4, the fuel discharge passage 32 is formed linearly in the cylinder head 12 and has a communication port 32 a with the fuel pressurizing chamber 30. A long hole fuel chamber 33 having a larger passage area than the fuel discharge passage 32 is formed on the downstream side of the fuel discharge passage 32 formed in the cylinder head 12, and a check valve 44 is accommodated in the fuel chamber 33. Yes. An accommodation hole 34 having a larger passage area than the fuel chamber 33 is formed on the fuel downstream side of the fuel chamber 33. The accommodation hole 34 opens in the outer peripheral wall of the cylinder head 12 to form a fuel outlet 34a. The fuel discharge passage 32, the fuel chamber 33, and the accommodation hole 34 constitute a fuel pressure feeding passage. The connecting member 41 for connecting the fuel pipe is accommodated in the accommodation 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 on substantially the same straight line as the fuel discharge passage 32.
[0018]
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 that biases the valve member 45 toward the valve closing side. Yes. The check valve 44 prevents 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 through the fuel discharge passage 32. The connecting member 41 is connected to a common rail as a stock pressure member (not shown) through a fuel pipe, 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 in the same manner as the cylinder head 12 and 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.
[0019]
The inner gear type feed pump 50 pressurizes 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 regulator valve (not shown) is opened, and excess fuel is returned to the fuel tank.
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 according to the engine operating state. Yes.
[0020]
Next, the mating surfaces of 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 substantially cylindrical aluminum member, and has a substantially arc-shaped close contact portion 62 and an 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. The contact portion 62 has a plurality of bolt holes 64, and the bolts 70 shown in FIG. 3 are screwed into the plurality of bolt holes 64. When the bearing cover 60 is fixed to the housing body 11 by tightening the bolts 70, the contact portion 62 is in close contact with the mating surface on the housing body 11 side. At this time, the recessed portion 61 is located in the vicinity of the fitting hole 11 a of the cylinder heads 12 and 13. A stepped portion 63 is formed at a boundary portion between the contact portion 62 and the recessed portion 61 where a predetermined surface pressure is generated by screw tightening of the bolt 70, and the stepped portion 63 has a height of 0.2 mm to Since it is about 1.0 mm, the recessed part 61 does not contact 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 a dimension that does not allow the recessed portion 61 to contact the mating surface of the housing body 11. The recessed portion 61 and the stepped portion 63 constitute contact escape means.
[0021]
Next, the operation of the fuel injection pump 10 will be described.
As the drive shaft 14 rotates, the cam 17 rotates, and as the cam 17 rotates, the shoe 18 revolves without rotating. As the shoe 18 revolves, the planar contact surfaces formed on the shoe 18 and the plunger 20 slide to move the plunger 20 back and forth.
[0022]
When the plunger 20 at the top dead center is lowered 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 supplied from the fuel inflow passage 31 to the check valve 23. After that, the fuel flows into the fuel pressurizing chamber 30. When the plunger 20 that has reached the bottom dead center rises again toward the top dead center, the check valve 23 closes and the fuel pressure in the fuel pressurizing chamber 30 rises. When the fuel pressure in the fuel pressurizing chamber 30 rises higher than the fuel pressure in the fuel passage 41a, the check valve 44 opens.
[0023]
The fuel pressurized in the fuel pressurizing chamber 30 on the cylinder head 12 side is sent 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 and is supplied from the fuel passage 41a to the common rail. The common rail accumulates the pressure-fluctuated fuel supplied from the fuel injection pump 10 and holds it at a constant pressure. High pressure fuel is supplied from a common rail to an injector (not shown).
[0024]
Next, a bearing cover of a comparative example will be described with reference to FIGS. 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 in the first embodiment. The same reference numerals are assigned to substantially the same components.
[0025]
As shown in FIGS. 7 and 8, the bearing cover 160 is provided with a substantially annular close contact portion 162 on the mating surface with the housing body 11. The contact portion 162 has a plurality of bolt holes 164, and the bolts 70 of the first embodiment shown in FIG. When the bearing cover 160 is fixed to the housing body 11 by tightening the bolts 70, the contact portion 162 is in close contact with the mating surface on the housing body 11 side. At this time, since the bolt hole 164 cannot be disposed in the region near the fitting hole 11a of the cylinder heads 12 and 13, the surface pressure due to the tightening force of the bolt 70 does not reach a predetermined surface pressure in this region. The surface pressure of the mating surface between the bearing cover 160 and the housing body 11 decreases. Further, since the housing main body 11 holds the cylinder heads 12 and 13 that form the fuel pressurizing chamber 30, when the plunger 20 is raised and the fuel is pressurized and pumped, the housing main body 11 causes the cylinder heads 12 and 13 to move. Receive tensile force through. For this reason, a slight repeated relative slip accompanied by a frictional force occurs in the low surface pressure portion between the bearing cover 160 and the housing main body 11, and there is a possibility that fretting wear may occur.
[0026]
When fretting wear occurs, the generated wear powder is not easily discharged from the mating surface between the bearing cover 160 and the housing main body 11, which significantly affects the wear and frictional behavior of the bearing cover 160 and the housing main body 11. Cause local friction and large frictional force. Accordingly, at the fretting operation position, which is the area near the fitting hole 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 leakage occurs. There is a problem that there is a risk of doing.
[0027]
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 11 so that the bolts 70 for fixing the bearing cover 60 to the housing main body 11 cannot be arranged. In this case, even if the housing body 11 receives a pulling force via the cylinder heads 12 and 13 due to the pressurization / pumping of the fuel by the plunger 20, by providing a predetermined clearance on the mating surface of the bearing cover 60 and the housing body 11, A low surface pressure portion where the surface pressure due to the tightening force of the bolt 70 does not reach a predetermined surface pressure is eliminated, and a slight repeated relative slip with a frictional force is prevented from occurring between the bearing cover 60 and the housing body 11. . Therefore, fretting wear is prevented from occurring on the mating surface of the bearing cover 60 and the housing body 11, and the bolt 70 is loosened or broken, and the plunger 20 is seized, or fuel leakage occurs. And can improve reliability.
[0028]
Further, in the first embodiment, the housing body 11 and the bearing cover 60 are made smaller in size, and it becomes easy to secure the mounting space by reducing the occupied space of the fuel injection pump 10, and the housing body 11 and the bearing. By forming the cover 60 with a relatively low hardness metal such as aluminum, the weight of the fuel injection pump 10 can be reduced, and it becomes easy to meet the demands for reducing fuel consumption.
[0029]
Furthermore, in the first embodiment, the occurrence of fretting wear can be easily prevented with a relatively simple configuration 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 manufacturing, and reduce manufacturing costs.
[0030]
In the first embodiment described above, the recessed portion 61 is provided on the mating surface on the bearing cover 60 side. However, the recessed portion may be provided on the mating surface on the housing body 11 side. You may provide a recessed part in the mating surface of both sides.
[0031]
(Second embodiment)
A second embodiment is shown in FIG. Components that are substantially the same as those of the first embodiment shown in FIG.
As shown in FIG. 5, the bearing cover 80 of the second embodiment is provided with a protrusion 81 in the recess 61. The protrusion 81 is provided so that a virtual line connecting the protrusions 81 passes through the approximate 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 stepped portion 63. The protrusion 81 can contact the mating surface on the housing body side.
[0032]
In the second embodiment, the same effect as that of the first embodiment shown in FIG. 2 can be obtained. Further, since the protrusion 81 that can contact the mating surface on the housing body side is provided in the recess 61, the protrusion 81 serves as a fulcrum when the fuel is pressurized and pumped by the plunger. Is prevented, and the bearing cover 80 is prevented from being deformed. Therefore, the seizure of the plunger and the occurrence of fuel leakage can be reliably prevented. In the second embodiment, it is conceivable that the protrusion 81 is worn during the pressurization / pumping of the fuel by the plunger, but the generated wear powder 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 occurrence of fretting wear.
[0033]
(Third embodiment)
A third embodiment is shown in FIG.
The plate member 90 of the third embodiment shown in FIG. 6 is provided on the mating surface between the bearing cover 160 and the housing body 11 of the comparative example shown in FIGS. 7 and 8. The plate member 90 is a pair of arc-shaped members and has a plurality of bolt holes 94. The bolt hole 94 is formed at a position overlapping the bolt hole 164 of the bearing cover 160. 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 is in close contact with the mating surface on the bearing cover 160 side, and the other The portion 96 is in 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 main body 11, and this predetermined clearance is located near the fitting hole of the cylinder head.
[0034]
In the third embodiment, the same effect as that of the first embodiment shown in FIG. 2 can be obtained. Furthermore, 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, facilitate manufacturing, and reduce manufacturing costs.
[Brief description of the drawings]
FIG. 1 is a cross-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 the 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 the fuel injection pump according to the first embodiment of the present invention.
4 is a cross-sectional view taken along line IV-IV in FIG.
FIG. 5 is a front view showing a mating surface on the 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 cross-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 the 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 pressurization chamber 31 Fuel inflow passage 32 Fuel discharge passage (fuel pressure feed passage)
33 Fuel chamber (fuel pressure feed passage)
60, 80 Bearing cover (support member)
61 Recessed part (contact escape means)
62 Contact part 63 Step part (contact escape means)
70 Bolt 81 Projection 90 Plate member

Claims (4)

A drive shaft;
A cam that rotates with the drive shaft;
A movable member disposed on the outer periphery of the cam, pressurizing the fuel sucked into the fuel pressurizing chamber by reciprocating in the vertical direction with respect to the drive shaft as the cam rotates, and delivering the pressurized fuel to the fuel pumping passage; ,
An element that has the fuel pumping passage and supports the movable member so as to be reciprocally movable in a direction perpendicular to the drive shaft ;
A housing body having a fitting hole into which the element can be fitted, and holding the element on an inner wall of the fitting hole;
Is fixed in contact with the end portion in the axial direction of the drive shaft for the housing body, a support member for rotatably supporting the drive shaft,
Contact escape means provided on a mating surface of the housing body and the support member in a direction perpendicular to the axial direction of the drive shaft, and having a predetermined clearance;
A fuel injection pump comprising:   2. The fuel injection pump according to claim 1, wherein the contact escape means has a recess provided on the mating surface on one side or both sides of the housing body and the support member.   3. The fuel injection pump according to claim 2, wherein the contact escape means includes a protrusion provided in the recess and capable of contacting the housing body or the mating surface on the support member side.   2. The fuel injection pump according to claim 1, wherein the contact escape means includes a plate member provided on the mating surface and capable of being in close contact with the housing body and the support member.

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