JP2020165346A - Fuel pump - Google Patents

Abstract

To provide a fuel pump where a Hertz surface pressure applied onto a contact area between a pressing part of a lifter for following the rotation of a cam and the end on the plunger side is reduced to suppress the slide, thus improving the durability.SOLUTION: In a fuel pump (50) for pressurizing and discharging fuel with the reciprocation of a plunger via a lifter (63) by the rotation of a cam (61c), a plunger side contact curved face (60C) at one end (60p) of the plunger (60) and a lifter side contact curved face (63C) of a pressing part of the lifter have contact with each other, and one contact curved face (60C) out of the plunger side contact curved face (60C) and the lifter side contact curved face (63C) forms a convex spherical surface (60Cv) and the other contact curved face (63C) forms a pair of concave spherical surfaces (63Cc, 63Cc) symmetrical with respect to a plunger center axis (Cp). The concave spherical surfaces (63Cc, 63Cc) each have a larger curvature radius than the convex spherical surface (60Cv).SELECTED DRAWING: Figure 5

Description

The present invention relates to a fuel pump that pressurizes and discharges fuel in a pressurizing chamber by reciprocating a plunger.

A fuel pump in which the plunger reciprocates when the end of the plunger comes into contact with the lifter that follows the rotation of the cam is particularly common as a high-pressure fuel pump (see, for example, Patent Document 1).

JP-A-2010-196641

The high-pressure fuel pump disclosed in Patent Document 1 has a pump chamber (pressurizing chamber) above a plunger that reciprocates up and down, and changes the volume of the pump chamber by the reciprocating motion of the plunger to supply fuel in the pump chamber. Pressurize and discharge.

The lower end of the plunger is in contact with the outer end surface of the lid of the covered cylindrical guide.
A drive body (lifter) is slidably fitted in the cylinder portion of the guide body, and the upper end portion of the drive body is in contact with the inner end surface of the lid portion of the guide body.
A roller pivotally supported at the lower end of the drive body is in contact with the cam surface on the outer circumference of the cam in which the two cam noses are formed at intervals of 180 degrees from above.

When the cam nose pushes up the drive body (lifter) via the roller due to the rotation of the cam, the plunger is pushed up together with the guide body in contact with the drive body, and the fuel in the pump chamber is pressurized and discharged.
When the cam nose is separated from the roller by the rotation of the cam, the plunger is pushed back downward by the spring, and fuel is sucked into the pump chamber.

The inner end surface of the lid of the guide has a concave spherical surface (concave spherical surface), and the upper end surface of the drive body in contact with the concave spherical surface has a convex spherical surface (convex spherical surface), and the concave spherical surface of the guide body. Has a larger radius of curvature than the convex spherical surface of the driving body, and is in point contact at one point in the center.

Since the pressure (Hertz surface pressure) applied to the elastic contact portion between the spherical surface and the spherical surface is in point contact at one point, it becomes a large pressure close to the permissible limit value of the contact surface, and there is a problem in durability.
Further, since the drive body is separated from the guide body except that the drive body makes point contact with the guide body at one point, the drive body is allowed to tilt slightly with respect to the guide body, and therefore contacts when the drive body tilts. The points move, and the pressing direction of the drive body is not perpendicular to the tangent line at the contact point of the spherical surface, so that slippage occurs and wear easily, and durability remains a problem.

The present invention has been made in view of this point, and an object of the present invention is to reduce the Hertz surface pressure applied to the contact portion between the pressing portion of the lifter following the rotation of the cam and the end portion on the plunger side, and slip. The point is to provide a fuel pump that can improve the durability by suppressing the above.

In order to achieve the above object, the present invention
In a fuel pump in which one end of a plunger comes into contact with a pressing portion of a lifter that follows the rotation of a cam on a pump cam shaft, and the plunger reciprocates via the lifter due to the rotation of the cam to pressurize and discharge fuel. ,
The plunger-side contact curved surface at one end of the plunger and the lifter-side contact curved surface of the pressing portion of the lifter are in contact with each other.
In the plunger-side contact curved surface and the lifter-side contact curved surface, one contact curved surface forms a convex spherical surface, and the other contact curved surface forms a pair of concave spherical surfaces symmetrical with respect to the plunger central axis, which is the central axis of the plunger.
The concave spherical surface provides a fuel pump characterized by having a larger radius of curvature than the convex spherical surface.

According to this configuration, the plunger-side contact curved surface of the plunger that is in contact with each other and the lifter-side contact curved surface of the lifter that follows the rotation of the cam of the pump cam shaft have one contact curved surface forming a convex spherical surface and the other contact curved surface being the plunger center. Since a pair of concave spheres that are symmetric with respect to the axis are formed, and the concave sphere has a larger radius of curvature than the convex sphere, the convex sphere makes point contact with each pair of concave spheres that are symmetric with respect to the central axis of the plunger, that is, at one point. The point contact is made at two points, and the pressure (Hertz surface pressure) applied to the elastic contact part of the convex spherical surface and the concave spherical surface is halved as compared with the case of point contact at one point, so that the high pressure fuel pump 50 Durability is improved.

Further, even if the lifter is slightly tilted with respect to the plunger, the convex spherical surface is maintained in contact with the pair of concave spherical surfaces at two points and slippage is suppressed, so that the wear resistance is excellent.
Therefore, the durability of the high-pressure fuel pump 50 is further improved by reducing the Hertz surface pressure and increasing the wear resistance.

In a preferred embodiment of the invention
The contact angle formed by the tangent line at each contact point between the convex spherical surface and the pair of concave spherical surfaces with respect to the central axis of the plunger is 45 degrees or more and 65 degrees or less.

According to this configuration, the contact angle formed by the tangents at each contact point between the convex spherical surface and the pair of concave spherical surfaces with respect to the central axis of the plunger is set to 45 degrees or more and 65 degrees or less, thereby reducing the Hertz surface pressure. It is possible to maintain point contact at two points without difficulty, and it is possible to suppress slippage as much as possible, increase wear resistance, and improve the durability of the high-pressure fuel pump.

In a preferred embodiment of the invention
The plunger is pressed and urged against the lifter by a spring.
The spring is provided so as to act on the other end of one end of the plunger opposite to the plunger-side contact curved surface.

According to this configuration, the spring that presses and urges the plunger to the lifter acts on the other end of the plunger on the opposite side to the plunger side contact curved surface, so that the load receiving surface and the spring due to fuel compression on the plunger are applied. The return load receiving surface (the end surface of the other end on the opposite side of the plunger side contact curved surface of the plunger) is almost the same, the behavior of the plunger is stable against the change of load due to the movement of the plunger, and the durability of the spherical surface is stable. Can be further enhanced.
Further, the spring acting on the end portion of the plunger opposite to the contact curved surface on the plunger side is provided in the pressurizing chamber, so that the fuel pump can be miniaturized.

In a preferred embodiment of the invention
The plunger is in a posture in which the central axis of the plunger is oriented in the vertical direction, and the contact curved surface on the plunger side at the lower end thereof forms the convex spherical surface.
The lifter-side contact curved surface of the pressing portion located above the lifter forms a pair of concave spherical surfaces.
The pressing portion of the lifter includes a recess recessed downward between the pair of concave spherical surfaces.

According to this configuration, the plunger is in a posture in which the central axis of the plunger is oriented in the vertical direction, and the contact curved surface on the plunger side at the lower end thereof forms the convex spherical surface, and the contact on the lifter side of the pressing portion located above the lifter. Since the curved surface forms a pair of concave spherical surfaces and the lifting portion of the lifter is provided with a concave portion recessed downward between the pair of concave spherical surfaces, oil collects in the concave portion of the pressing portion of the lifter to improve lubricity and wear. Can be reduced and durability can be improved.

In a preferred embodiment of the invention
The cam is a disc-shaped eccentric cam.
The lifter is externally rotatably mounted on the outer peripheral surface of the eccentric cam.
The lifter has a weight portion on the side opposite to the pressing portion with respect to the rotation center axis of the pump cam shaft.

According to this configuration, the lifter externally rotatably mounted on the outer peripheral surface of the disk-shaped eccentric cam has a weight portion on the opposite side of the pressing portion with respect to the rotation center axis of the pump cam shaft, so that the lifter has an external force. As long as the weight is not added, the weight portion is swiveled downward and the pressing portion on the opposite side is positioned on the upper side, so that the assembling property of the fuel pump can be improved.

In the present invention, the plunger-side contact curved surface of the plunger that is in contact with each other and the lifter-side contact curved surface of the lifter that follows the rotation of the cam of the pump cam shaft have one contact curved surface forming a convex spherical surface and the other contact curved surface being the central axis of the plunger. Since the concave sphere has a larger radius of curvature than the convex sphere, the convex sphere makes point contact with each pair of concave spheres symmetric with respect to the central axis of the plunger, that is, at one point. The point contact is made at two points, and the pressure (Hertz surface pressure) applied to the elastic contact portion of the convex spherical surface and the concave spherical surface is halved as compared with the case of the point contact at one point.

Further, even if the lifter is slightly tilted with respect to the plunger, the convex spherical surface is maintained in contact with the pair of concave spherical surfaces at two points, and slippage is suppressed, so that the wear resistance is excellent.
Therefore, the durability of the fuel pump can be improved by reducing the Hertz surface pressure and excellent wear resistance.

It is an overall side view of the motorcycle which concerns on one Embodiment of this invention. It is a right side view of a cylinder head and a high pressure fuel pump. It is sectional drawing of the cylinder head and a high pressure fuel pump by the arrow III-III of FIG. FIG. 3 is a cross-sectional view of a cylinder head and a high-pressure fuel pump as viewed from the IV-IV arrow in FIG. It is an enlarged view of the contact part of a plunger and a lifter in FIG. It is a graph which shows the change of the Hertz surface pressure with respect to a contact angle.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS. 1 to 6.
FIG. 1 is a right side view of a motorcycle 1 which is a saddle-mounted vehicle equipped with an internal combustion engine 3 provided with a high-pressure fuel pump 50 according to an embodiment to which the present invention is applied.

In the description of the present specification, the front-rear, left-right directions are based on the usual reference that the straight-ahead direction of the motorcycle 1 according to the present embodiment is the front, and in the drawings, FR is the front and RR is the rear. , LH indicates the left side, and RH indicates the right side.
However, the terms anterior and posterior in the present specification do not mean anterior and posterior in the strict sense, but roughly anterior and posterior.
Further, when the term "upper" is used in the present specification, it also means "upper".

The body frame 2 of the motorcycle 1 is a pivot frame in which the main frame 21 is rearwardly covered by the fuel tank 16 from the upper part of the head pipe 20, extends slightly downward, and then bends downward. It forms 21a.
From the head pipe 20, the down frame 22 extends diagonally backward and downward in the center of the vehicle width direction.

The front part of the crankcase 30 in the internal combustion engine 3 is attached to the support bracket 22a at the lower part of the down frame 22 by hanger bolts 3a at two places above and below, and the rear part of the crankcase 30 is attached to the pivot frame 21a by hanger bolts 3b. The internal combustion engine 3 is supported by the vehicle body frame 2.
A pair of left and right seat rails 23 (not shown) extend rearward from the bent portion of the main frame 21, and a back stay 24 connecting the seat rail 23 and the central portion of the pivot frame 21a supports the seat rail 23. ..

A front fork 10 is pivotally supported by the head pipe 20, a front wheel 11 is pivotally supported at the lower end thereof, and a steering handle 12 is provided at the upper end of the pivot shaft of the front fork 10.
The rear fork 13 whose front end is pivotally supported by the pivot shaft 25 provided at the lower part of the pivot frame 21a extends rearward, and the rear wheel 14 is pivotally supported at the rear end, and the central portion of the rear fork 13 and the back stay 24 A rear cushion (not shown) is installed between the two.
The fuel tank 16 is erected on the main frame 21 so as to straddle the left and right sides, and the seat 18 is supported by the seat rail 23 behind the fuel tank 16.
A low-pressure fuel pump 17 is installed in the fuel tank 16.

The internal combustion engine 3 mounted on the motorcycle 1 is an air-cooled single-cylinder SOHC type 4-stroke cycle internal combustion engine.
The internal combustion engine 3 is integrally provided with a multi-speed transmission in the rear portion of the crankcase 30 to form a so-called power unit, and the crankshaft 31 is oriented in the vehicle width direction of the motorcycle 1, that is, in the left-right direction. It is supported by the vehicle body frame 2.

In the internal combustion engine 3, the cylinder block 33 and the cylinder head 34 are sequentially stacked diagonally above the crankcase 30, and the cylinder axis Lc, which is the central axis of the cylinder bore of the cylinder block 33, is oriented in a substantially vertical direction in which the cylinder axis Lc is slightly tilted forward. It stands up from the crankcase 30 in a forward leaning posture.
The cylinder head cover 35 covers the upper part of the cylinder head 34.

The intake pipe 40 extends from the rear surface of the cylinder head 34, and the throttle body 41 is interposed in the intake pipe 40.
The fuel injection valve 43 provided along the intake pipe 40 has an injection port at the tip facing the combustion chamber.
The exhaust pipe 45 extending from the front surface of the cylinder head 34 extends rearward on the lower right side of the vehicle and is connected to the muffler 46.

A high-pressure fuel pump 50 is provided on the right side portion of the cylinder head 34 of the internal combustion engine 3 in the vehicle width direction.
The high-pressure fuel pump 50 is a fuel pump that pressurizes and discharges the fuel supplied from the low-pressure fuel pump 17 in the fuel tank 16 by the reciprocating motion of the round bar-shaped plunger 60, and is discharged from the high-pressure fuel pump 50. The high-pressure fuel is sent to the fuel injection valve 43, and the high-pressure fuel is directly injected from the fuel injection valve 43 into the combustion chamber.

With reference to FIGS. 3 and 4, the pump housing 51 of the high-pressure fuel pump 50 is filled with a plunger hole 52 in which the plunger 60 reciprocates, a pressurizing chamber 53 in which fuel is pressurized by the plunger 60, and fuel. A fuel suction passage 54 sucked into the pressure chamber 53, a fuel discharge passage 55 from which the fuel pressurized in the pressure chamber 53 is discharged, and the like are formed.
A discharge valve 55v that opens at a predetermined pressure or higher is provided in the downstream end discharge passage portion 55z at the rear end of the fuel discharge passage 55.

The high-pressure fuel pump 50 drives the suction valve 73 interposed in the middle of the fuel suction passage 54 to adjust the amount of fuel discharged from the pressurizing chamber 53, and the suction valve drive device 70 and the suction of the fuel suction passage 54. A disk-shaped pulsation damper 80, which is interposed upstream of the valve 73 and reduces the pulsation of fuel pressure, is incorporated in the pump housing 51 (see FIG. 2).

With reference to FIG. 3, the camshaft 36 is supported by the cylinder head 34 in the vehicle width direction, and the camshaft 36 is cranked by a cam churn (not shown) hung from the crankshaft 31. The rotation of the shaft 31 is transmitted and rotates.
The pump cam shaft 61 is coaxially connected to the right end of the cam shaft 36 and rotates integrally.

The pump housing 51 is divided into upper and lower parts in the direction of the cylinder axis Lc, and is overlapped with the upper mating surface of the cylinder head 34, and covers the pump cam shaft 61 except for the lower portion of the plunger hole 52, and the lower housing portion 51L and the lower housing. It is composed of an upper housing portion 51U which is overlapped with the upper mating surface of the portion 51L and forms the plunger hole 52, the pressurizing chamber 53, the damper chamber 56 of the pulsation damper 80, and the like.
The disk-shaped pulsation damper 80 is housed in a damper chamber 56 covered by a damper lid member 85.

With reference to FIG. 3, a plunger hole 52 in which the plunger 60 reciprocates is formed above the pump cam shaft 61 of the pump housing 51, which is the central axis of the plunger hole 52, and also the central axis of the round bar-shaped plunger 60. A plunger central axis Cp is parallel to the cylinder axis Lc.

With reference to FIGS. 3 and 4, the central shaft of the pump cam shaft 61 is on the mating surfaces of the cylinder head 34 and the lower housing portion 51L, and the left and right ends of the pump cam shaft 61 are the cylinder head 34 and the lower housing portion 51L. It is rotatably supported by ball bearings 62 and 62 sandwiched between portions 51L.

An eccentric cam 61c is formed between the ball bearings 62 and 62 of the pump cam shaft 61.
The eccentric cam 61c has an outer peripheral circumferential surface eccentric from the central axis of the pump cam shaft 61, and the lifter 63 is externally rotatably mounted on the outer peripheral circumferential surface via a needle bearing 64.

The lifter 63 has an inner peripheral surface that forms a circumferential surface that fits into the outer race of the needle bearing 64, and has a pressing portion 63p that projects radially outward at a narrow central angle and bulges outward at a relatively wide central angle. The weight portion 63w is formed at a position symmetrical with respect to the central axis of the inner peripheral surface.

Therefore, when the lifter 63 is mounted on the pump cam shaft 61 horizontally oriented in the vehicle width direction via the needle bearing 64, the weight portion 63w naturally lowers the weight portion 63w and the pressing portion 63p is moved upward due to the weight of the weight portion 63w. It is possible to easily assemble the fuel pump 50 by bringing the lower end portion 60p of the plunger 60 into contact with the pressing portion 63p located above, and to improve the assembling property of the fuel pump. it can.

FIG. 5 shows an enlarged view of a contact portion (enlarged view of a main part in FIG. 4) in which the lower end portion 60p of the plunger 60 contacts the pressing portion 63p facing upward of the lifter 63 from above.
With reference to FIGS. 5 and 4, the plunger-side contact curved surface 60C to which the pressing portion 63p of the lifter 63 of the lower end portion 60p of the plunger 60 contacts forms a convex spherical surface 60Cv protruding downward.

On the other hand, the lifter-side contact curved surface 63C to which the lower end 60p of the plunger 60 of the pressing portion 63p of the lifter 63 contacts forms a concave spherical surface 63Cc recessed downward.
The lifter side contact curved surface 63C is composed of a pair of front and rear concave spherical surfaces 63Cc and 63Cc that are symmetrical with respect to the plunger central axis Cp in the axial direction of the pump cam shaft 61 shown in FIG.

The radius of curvature Rc of the concave spherical surfaces 63Cc and 63Cc of the lifter side contact curved surface 63C at the pressing portion 63p of the lifter 63 is larger than the radius of curvature Rv of the convex spherical surface 60Cv of the plunger side contact curved surface 60C at the lower end portion 60p of the plunger 60.

As shown in FIG. 4, the convex spherical surface 60Cv, which is the plunger-side contact curved surface 60C of the lower end portion 60p of the plunger 60, becomes a pair of concave spherical surfaces 63Cc, 63Cc, which are the lifter-side contact curved surfaces 63C of the pressing portion 63p of the lifter 63. The lifter 63 is restrained from rotating by being sandwiched between the two points.
Therefore, even if the eccentric cam 61c of the pump cam shaft 61 rotates, the lifter 63 makes a circular motion including vertical movement while its rotation is suppressed.

The pressing portion 63p of the lifter 63 includes a recess 63d recessed downward between a pair of front and rear concave spherical surfaces 63Cc and 63Cc.
The recess 63d is located on the central axis Cp of the plunger, and its U-shaped inner surface is continuously formed on the front and rear concave spherical surfaces 63Cc and 63Cc.

Therefore, the pair of concave spherical surfaces 63Cc and 63Cc opened upward receive the oil transmitted through the outer peripheral surface of the plunger 60 and the oil falling from above, and the received oil flows downward along the concave spherical surfaces 63Cc and 63Cc and is centered. It collects in the recess 63d of.
Since the pressing portion 63p of the lifter 63 and the lower end portion 60p of the plunger 60 are in contact with each other and reciprocate up and down, the oil accumulated in the recess 63d always lubricates the lifter side contact curved surface 63C and the plunger side contact curved surface 60C, and has lubricity. The improvement can smooth the movement of the lifter and the plunger, reduce wear, and improve durability.

Most of the plunger holes 52 formed in the pump housing 51 are formed in the upper housing portion 51U, and the lower portion is formed in the lower housing portion 51L.
A cylindrical plunger guide 65 is fitted into the plunger hole 52 of the upper housing portion 51U, and the plunger 60 is slidably fitted into the plunger guide 65.

The plunger 60 reciprocates in the vertical direction guided by the plunger guide 65, and the lower part of the plunger 60 penetrates the lower part of the plunger hole 52 of the lower housing portion 51L and is rotatably mounted on the pump cam shaft 61. It is in contact with the pressing portion 63p facing upward of 63.
The space above the plunger hole 52 of the upper housing portion 51U is a pressurizing chamber 53, and a compression spring 66 is interposed between the ceiling surface of the pressurizing chamber 53 and the upper end portion 60u of the plunger 60.

Therefore, the plunger 60 receives both the spring force of the compression spring 66 and the pressure of the pressurizing chamber 53 at the upper end portion 60u and is urged downward, and the lower end portion 60p of the plunger 60 presses the pressing portion 63p of the lifter 63 from above. Press.

The pump body of the high-pressure fuel pump 50 has the above structure, and when the pump cam shaft 61 rotates integrally with the cam shaft 36, the rotation of the eccentric cam 61c causes a pair of concave spherical surfaces of the pressing portion 63p of the lifter 63. When 63Cc and 63Cc come into contact with each other at two points so as to sandwich the convex spherical surface 60Cc at the lower end 60p of the plunger 60, the lifter 63 suppresses its own rotation and makes a circular motion to reciprocate up and down. The plunger 60, which is urged and contacted by the compression spring 66 from above to the pressing portion 63p of the above, can be reciprocated up and down to pressurize and discharge the fuel in the pressurizing chamber 53.

With reference to FIG. 5, which is an enlarged view of the contact portion between the plunger 60 and the lifter 63, the radius of curvature Rv of the convex spherical surface 60Cv at the lower end 60p of the plunger 60 of the high-pressure fuel pump 50 is 3.0 (+0.05 / 0 tolerance) mm, the radius (radius of curvature) Rc of the concave spherical surface 63Cc of the pressing portion 63p of the lifter 63 is 3.5 (+ 0.2 / -0.05 tolerance) mm, and the radius of curvature of the convex spherical surface 60Cv. The radius of curvature Rc of the concave spherical surface 63Cc is larger than Rv.

Convex sphere 60Cv at the lower end 60p of the plunger 60 and tangent Lx at each contact point X of the pair of concave spheres 63Cc and 63Cc of the pressing portion 63p of the lifter 63 with respect to the contact angle θ with respect to the plunger central axis Cp. FIG. 6 shows changes in the Hertz surface pressure Ph, which is the pressure applied to the elastic contact portion between 60 Cv and the concave spherical surface 63 Cc.

With reference to FIG. 5, for the plunger 60 and the lifter 63 of the present embodiment, the fuel pressure in the pressurizing chamber 53 applied to the plunger 60 is 20 MPa, the spring load of the compression spring 66 is 20.1 N, and the total load f. Is applied to the lifter 63, and the contact point X of the concave spherical surface 63Cc of the lifter 63 is obtained by calculating the Hertz surface pressure Ph shown in FIG. 6, assuming that a load of f / sin θ is applied perpendicular to the tangent line Lx. ing.

As shown in the graph of FIG. 6, the Hertz surface pressure Ph becomes the minimum when the contact angle θ formed by the tangent line Lx at the contact point X with respect to the plunger central axis Cp is about 55 degrees. ..
Therefore, in the present embodiment, the contact angle θ formed by the tangent line Lx at the contact point X with respect to the plunger central axis Cp is 55 degrees, and the Hertz surface pressure Ph is minimized.

As described above, in the high-pressure fuel pump 50, the convex spherical surface 60Cv at the lower end 60p of the plunger 60 contacts the pair of concave spherical surfaces 63Cc and 63Cc symmetrical with respect to the plunger central axis of the pressing portion 63p of the lifter 63, respectively. The pressure (Hertz surface pressure) applied to the elastic contact parts of the convex spherical surface 60Cv and the concave spherical surfaces 63Cc and 63Cc by making point contact at one point, that is, by making point contact at two points, is when point contact is made at one point. Compared to half.
Further, each Hertz surface pressure Ph is minimized by setting the contact angle θ formed by the tangent line Lx at the contact point X with respect to the plunger central axis Cp to 55 degrees.

Therefore, the Hertz surface pressure Ph is significantly reduced, and the durability of the high-pressure fuel pump 50 can be improved.
Further, even if the lifter 63 is slightly tilted with respect to the plunger 60, the convex spherical surface 60Cc is maintained in contact with the pair of concave spherical surfaces 63Cc and 63Cc at two points to suppress slippage, so that wear resistance is increased. As a result, the durability of the high-pressure fuel pump 50 is further improved.

As shown in FIGS. 3 and 4, the compression spring 66 that presses and urges the plunger 60 against the lifter 63 acts on the upper end portion 60u of the plunger 60 opposite to the plunger side contact curved surface 60C, and thus acts on the upper end portion 60u of the plunger 60 with respect to the plunger 60. The load receiving surface due to fuel compression and the return load receiving surface due to the compression spring 66 (the end surface of the upper end 60u on the opposite side of the plunger side contact curved surface 60C of the plunger) are substantially the same, and the load is switched due to the movement of the plunger 60. On the other hand, the behavior of the plunger 60 is stable.

By stabilizing the movement of the plunger 60, the durability of the contact portion between the convex spherical surface 60Cc of the plunger 60 and the pair of concave spherical surfaces 63Cc and 63Cc of the lifter 63 can be further enhanced.
Further, the compression spring 66 acting on the upper end portion 60u on the side opposite to the plunger side contact curved surface 60C of the lower end portion 60p of the plunger 60 will be provided in the pressurizing chamber 53 to reduce the size of the high pressure fuel pump 50. be able to.

There are various combinations of the radius of curvature Rv of the convex spherical surface 60Cv at the lower end 60p of the plunger 60 and the radius of curvature Rc of the concave spherical surface 63Cc of the pressing portion 63p of the lifter 63, and the smaller the difference in radius of curvature (Rc-Rv), the more. , The contact area is large and the Hertz surface pressure Ph is small.

On the arrangement of the concave spherical surface 63Cc of the lifter 63 with respect to the convex spherical surface 60Cv of the plunger 60, the shape of the pressing portion 63p of the lifter 63 prevents the contact curved surface of the convex spherical surface 60Cv from contacting the upper end corner of the concave spherical surface 63Cc. Therefore, there is a limit to the contact area, and therefore there is a lower limit to the radius of curvature difference (Rc-Rv).

In various practical combinations of the radius of curvature Rv of the convex sphere 60 Cv and the radius of curvature Rc of the concave sphere 63 Cc when the radius of curvature difference (Rc-Rv) is equal to or higher than the lower limit, the Hertz surface pressure Ph is minimized. With reference to FIG. 6, the contact angle θ formed by the tangent line Lx at the contact point X between the convex spherical surface 60 Cv and the concave spherical surface 63 Cc with respect to the plunger central axis Cp is in the range of 45 degrees or more and 65 degrees or less.

Therefore, by setting the contact angle θ to 45 degrees or more and 65 degrees or less, the Hertz surface pressure can be reduced, point contact at two points can be maintained reasonably, and slippage is possible. The wear resistance can be increased, and the durability of the high-pressure fuel pump 50 can be further improved.

Although the high-pressure fuel pump according to the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to the above embodiment, and is carried out in various embodiments within the scope of the gist of the present invention. It includes things.

Therefore, the present invention is not limited to high pressure fuel pumps.
The present invention is also applied to a fuel pump having a structure in which the lifter-side contact curved surface of the lifter pressing portion forms a convex spherical surface and the plunger-side contact curved surface at the end of the plunger forms a concave spherical surface.

Cp ... Plunger center axis, Lc ... Cylinder axis,
1 ... Motorcycle, 2 ... Body frame, 3 ... Internal combustion engine, 10 ... Front fork, 11 ... Front wheel, 13 ... Rear fork, 14 ... Rear wheel, 16 ... Fuel tank, 17 ... Low pressure fuel pump, 20 ... Head pipe, 21 ... main frame, 22 ... down frame, 23 ... seat rail,
30 ... crankcase, 31 ... crankshaft, 33 ... cylinder block, 33f ... cooling fins, 34 ... cylinder head, 34f ... cooling fins, 35 ... cylinder head cover, 36 ... camshaft,
40 ... intake pipe, 41 ... throttle body, 43 ... fuel injection valve, 45 ... exhaust pipe, 46 ... muffler,
50 ... High-pressure fuel pump, 51 ... Pump housing, 51L ... Lower housing, 51U ... Upper housing, 52 ... Plunger hole, 53 ... Pressurizing chamber, 54 ... Fuel suction passage, 55 ... Fuel discharge passage, 55v ... Discharge valve , 56 ... Damper room,
60 ... Plunger, 60u ... Upper end, 60p ... Lower end, 60C ... Plunger side contact curved surface, 60Cv ... Convex spherical surface, 61 ... Pump cam shaft, 61c ... Eccentric cam, 62 ... Ball bearing,
63 ... Lifter, 63p ... Pressing part, 63C ... Lifter side contact curved surface, 63Cc ... Concave spherical surface, 63d ... Recessed, 64 ... Needle bearing, 65 ... Plunger guide,
70 ... suction valve drive device, 73 ... suction valve, 80 ... pulsation damper, 85 ... damper lid member.

Claims (5)

One end (60p) of the plunger (60) comes into contact with the pressing portion (63p) of the lifter (63) that follows the rotation of the cam (61c) of the pump cam shaft (61), and the lifter is rotated by the rotation of the cam (61c). In the fuel pump (50), which pressurizes and discharges fuel by reciprocating the plunger via (63).
The plunger-side contact curved surface (60C) of one end (60p) of the plunger (60) and the lifter-side contact curved surface (63C) of the pressing portion of the lifter are in contact with each other.
In the plunger-side contact curved surface (60C) and the lifter-side contact curved surface (63C), one contact curved surface (60C) forms a convex spherical surface (60Cc) and the other contact curved surface (63C) is the plunger (60). A pair of concave spherical surfaces (63Cc, 63Cc) symmetrical with respect to the central axis (Cp) of the plunger, which is the central axis.
The concave spherical surface (63Cc, 63Cc) is a fuel pump characterized by having a larger radius of curvature than the convex spherical surface (60Cc). The contact angle (θ) formed by the tangent line (Lx) at each contact point (X) of the convex spherical surface (60Cc) and the pair of concave spherical surfaces (63Cc, 63Cc) with respect to the plunger central axis (Cp) is 45. The fuel pump according to claim 1, wherein the temperature is 65 degrees or more and 65 degrees or less. The plunger (60) is pressed and urged by the spring (66) against the lifter (63).
The spring (66) is provided so as to act on the other end (60u) of one end (60p) of the plunger (60) opposite to the plunger-side contact curved surface (60C). The fuel pump according to claim 1 or 2. The plunger (60) is in a posture in which the central axis (Cp) of the plunger is oriented in the vertical direction, and the contact curved surface (60C) on the plunger side of the lower end portion (60p) forms the convex spherical surface (60Cc).
The lifter-side contact curved surface (63C) of the pressing portion (63p) positioned above the lifter (63) forms a pair of concave spherical surfaces (63Cc, 63Cc).
Any one of claims 1 to 3, wherein the pressing portion (63p) of the lifter (63) is provided with a downwardly recessed recess between the pair of concave spherical surfaces (63Cc, 63Cc). The fuel pump described in the section. The cam (61c) is a disc-shaped eccentric cam (61c).
The lifter (63) is externally rotatably mounted on the outer peripheral surface of the eccentric cam (61c).
The fuel pump according to claim 4, wherein the lifter (63) has a weight portion (63w) on the side opposite to the pressing portion (63p) with respect to the rotation center axis of the pump cam shaft (61).

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