阅读说明：本技术 燃料喷射泵 (Fuel injection pump ) 是由 玉井直哉 于 2020-02-28 设计创作，主要内容包括：燃料喷射泵对燃料进行加压和喷射。凸轮(3)围绕凸轮的旋转轴线(Ax)旋转。壳体(2)包括容纳凸轮的凸轮室(21)以及连通至凸轮室的滑动室(22)。辊子(5)在与凸轮的表面接触的同时旋转。靴部(6)通过凸轮的旋转而在滑动室内往复运动并且与辊子的表面接触并在其表面上滑动。柱塞(7)与靴部一起往复运动。气缸(8)容纳柱塞并包括泵室(81)以通过柱塞的往复运动来对燃料进行加压和供给。变形部(4)是在凸轮的表面的一部分上沿凸轮的旋转轴线方向延伸的槽或突出部并且具有与凸轮的凸轮轮廓不同的形状。(The fuel injection pump pressurizes and injects fuel. The cam (3) rotates about a rotational axis (Ax) of the cam. The housing (2) includes a cam chamber (21) accommodating the cam and a slide chamber (22) communicating to the cam chamber. The roller (5) rotates while being in contact with the surface of the cam. The shoe (6) reciprocates in the sliding chamber by the rotation of the cam and is in contact with and slides on the surface of the roller. The plunger (7) reciprocates together with the shoe. The cylinder (8) accommodates a plunger and includes a pump chamber (81) to pressurize and supply fuel by reciprocating motion of the plunger. The deformation portion (4) is a groove or a protrusion extending in the rotational axis direction of the cam on a part of the surface of the cam and has a shape different from the cam profile of the cam.)

1. A fuel injection pump for pressurizing and injecting fuel, the fuel injection pump comprising:

a cam (3) configured to rotate about a rotational axis (Ax) of the cam and comprising a cam ridge;

a housing (2) configured to be supplied with lubricating oil and including a cam chamber (21) accommodating the cam and a slide chamber (22) communicating to the cam chamber;

a roller (5) configured to be in contact with and rotate on a surface of the cam;

a shoe (6) that is in contact with a surface of the roller on a side opposite to the cam and is configured to slide on the surface of the roller and is configured to reciprocate in the sliding chamber by rotation of the cam;

a plunger (7) configured to reciprocate together with the shoe;

a cylinder (8) that accommodates the plunger and includes a pump chamber (81) to pressurize and supply the fuel by a reciprocating motion of the plunger; and

a deformation portion (4) which is a groove or a protrusion formed on a part of a surface of the cam and extending in a direction of a rotational axis of the cam, the deformation portion having a shape different from a cam profile of the cam that contributes to pressurizing and supplying the fuel.

2. The fuel injection pump according to claim 1,

the pressure angle theta is the angle of the common normal (N) between the cam and the roller with respect to the axis (23) of the sliding chamber, and

the groove or the protrusion as the deformed portion is formed such that, when the cam rotates, a rate of change in the pressure angle in a state where the roller moves on the deformed portion provided on the surface of the cam is larger than a rate of change in the pressure angle in a state where the roller moves on a portion of the surface of the cam other than the deformed portion.

3. The fuel injection pump according to claim 1 or 2,

the cam includes a plurality of the cam ridges, an

The deformation portion is formed on each of the cam ridges.

4. The fuel injection pump according to claim 1 or 2,

the cam comprises two cam crests (31) at one side and the other side of the radial direction, respectively, each of the cam crests being a crest of the cam ridge, an

The deformation is formed on a cam base (32), which is the surface of the cam at the center between the two cam tops.

5. The fuel injection pump according to claim 1 or 2,

the process of said pressurizing and said supplying of said fuel comprises an intake stroke, a metering stroke, a compression stroke and a discharge stroke,

the plunger is configured to increase a volume of the pump chamber and cause the pump chamber to suck fuel in the suction stroke,

the plunger is configured to reduce a volume of the pump chamber in the metering stroke and pressurize and discharge the fuel while metering the fuel, and

the deformation portion is formed on the surface of the cam in a region (a) where the roller contacts the surface of the cam in the suction stroke.

6. The fuel injection pump according to claim 5,

the deformation is located on the surface of the cam in the region where the roller is in contact with the surface of the cam in the intake stroke and in a region (β) where the roller is in contact with the surface of the cam in the metering stroke, the compression stroke, and the discharge stroke.

7. The fuel injection pump according to claim 1 or 2,

the deformation portion is the groove extending in the direction of the rotation axis of the cam in a part of the surface of the cam, and

the relationship between the radius of curvature R of the deformation portion and the radius R of the roller is set in the range of R < R < R × 30.

Technical Field

The present disclosure relates to a fuel injection pump.

Background

A known fuel injection pump pressurizes fuel and the fuel is injected and supplied to an internal combustion engine or the like. The fuel injection pump converts a rotational motion of a cam driven by an internal combustion engine or an electric motor into a reciprocating motion of a plunger. The fuel injection pump further pressurizes fuel in a pump chamber located at a deep portion of a cylinder accommodating the plunger, and pressurizes and supplies the fuel. The fuel injection pump in patent document 1 includes a roller and a shoe between a cam and a plunger. The roller is in contact with a surface of the cam and is capable of rotating. The shoe holds the roller. The shoe includes an insertion member placed on the axis of the plunger and a base member placed outside the insertion member.

(patent document 1)

DE 10 2009 028 392-A1

The shoe portion includes two parts, which are a base member and an insertion member in the fuel injection pump in patent document 1. In addition, the fuel injection pump includes a base member as a part of the shoe portion. In order to reduce friction between the roller and the shoe at the time of start-up of the internal combustion engine, the base member is formed of a powder injection-molded body including a solid lubricating material. That is, in the fuel injection pump, many parts of the shoe portion become large, and thus the structure of the shoe portion is complicated. Therefore, the manufacturing cost thereof increases.

Disclosure of Invention

An object of the present disclosure is to provide a fuel injection pump in which friction between a roller and a shoe portion is reduced with a simple structure and to improve reliability of the fuel injection pump.

According to one aspect of the present disclosure, a fuel injection pump is configured to pressurize and inject fuel. The fuel injection pump includes a cam, a housing, a roller, a shoe, a plunger, a cylinder, and a deforming portion. The cam includes a cam ridge and is configured to rotate about a rotational axis of the cam. The housing includes a cam chamber accommodating the cam and a slide chamber communicating to the cam chamber. The lubricating oil is supplied to the housing. The roller is configured to rotate in contact with a surface of the cam. The shoe contacts and slides on the surface of the roller on the side opposite to the cam, and is configured to reciprocate in the sliding chamber by the rotation of the cam. The plunger is configured to reciprocate with the shoe. The cylinder accommodates a plunger and includes a pump chamber to pressurize and supply fuel by reciprocating motion of the plunger. The deformation portion is a groove or a protrusion extending in the rotational axis direction of the cam formed on a part of the surface of the cam and has a shape different from the cam profile that contributes to pressurizing and supplying the fuel.

According to this configuration, when the roller moves on the deformation portion formed in the surface of the cam by the rotation of the cam, an oil film is formed and held between the shoe and the roller by the squeezing effect, and the friction coefficient between the shoe and the roller is reduced. Therefore, the braking force by which the shoe brake roller rotates, hereinafter referred to as shoe braking torque, is smaller than the force by which the cam drive roller rotates, hereinafter referred to as cam driving torque. Therefore, the roller and the shoe are in a sliding state, and the cam and the roller are in a rolling state. Therefore, the fuel injection pump can protect the rollers from being stuck by reducing friction between the rollers and the shoe portion with a simple structure and has high reliability.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings. In the drawings:

fig. 1 is a sectional view showing a fuel injection pump according to a first embodiment.

Fig. 2 is a view showing the profile of the cam according to the first embodiment.

Fig. 3 is an enlarged view showing a portion indicated by III in fig. 2.

Fig. 4 is an enlarged view showing a portion indicated by IV in fig. 1.

Fig. 5A to 5D are explanatory diagrams showing a behavior of shifting the roller in the sliding state to the rolling state.

Fig. 6 is an explanatory diagram illustrating the radius of curvature of the deformed portion.

Fig. 7 is an explanatory view showing a curvature radius of the deformed portion.

Fig. 8 is a view showing the profile of a cam according to the second embodiment.

Fig. 9 is a view showing the profile of a cam according to the third embodiment.

Fig. 10 is a view showing the profile of a cam according to the fourth embodiment.

Fig. 11 is a view showing the profile of a cam according to the fifth embodiment.

Fig. 12 is a view showing the profile of a cam according to the sixth embodiment.

Detailed Description

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. The same reference numerals in the embodiments are assigned to the same or equivalent structures and the description thereof is omitted.

(first embodiment)

The first embodiment will be described with reference to the drawings. The fuel injection pump 1 in the present embodiment is configured to pressurize and supply fuel, such as light oil, that is injected and supplied to the internal combustion engine. The fuel is pressurized and supplied from the fuel injection pump 1, and is accumulated in the common rail. Subsequently, fuel is injected from a plurality of injectors connected to the common rail and supplied into cylinders of the internal combustion engine.

First, the structure of the fuel injection pump 1 will be described below. As shown in fig. 1, the fuel injection pump 1 includes a housing 2, a cam 3, a deforming portion 4 provided on the cam 3, a roller 5, a shoe 6, a plunger 7, a cylinder 8, and the like.

The housing 2 includes a cam chamber 21 and a slide chamber 22. The cam chamber 21 has a substantially cylindrical shape and is defined by an inner wall 211. The cam 3 is accommodated in the cam chamber 21 and is rotatable. The slide chamber 22 extends radially in one direction from the cam chamber 21. The cam chamber 21 communicates to the slide chamber 22. Lubricating oil is supplied to the cam chamber 21 and the slide chamber 22. The cam chamber 21 and the slide chamber 22 are filled with lubricating oil.

The cam 3 is accommodated in the cam chamber 21. The cam 3 receives torque transmitted from an unillustrated internal combustion engine or an unillustrated electric motor to an unillustrated camshaft and is rotationally driven around a rotational axis of the cam 3. The cam 3 comprises a plurality of cam ridges. The cam 3 in the first embodiment includes two cam ridges. In the drawings, reference numeral Ax denotes a rotation axis of the cam 3, and an arrow RD denotes a rotation direction of the cam 3.

Fig. 2 shows only the cam 3 assembled in the fuel injection pump 1 of the first embodiment. As shown in fig. 2, the peaks of the two cam ridges are hereinafter referred to as cam crests 31, respectively. The surfaces of the cams 3 which are located centrally between the two cam tops 31 are in the following referred to as cam bottoms 32 respectively. The cam ridge is also referred to as a cam lobe and the cam top 31 is also referred to as a cam nose. The cam top 31 is a portion of the surface of the cam 3 in which the radius of the cam 3 is the longest. The cam bottom 32 is a portion of the surface of the cam 3 where the radius of the cam 3 is shortest. The cam 3 in the first embodiment includes two cam crests 31 on one side and the other side in the radial direction, respectively. The two cam bottoms 32 are positioned in a direction orthogonal to a line connecting the two cam tops 31.

As shown in fig. 2 and 3, the deformation portion 4 is formed in a part of the surface of the cam 3. The surface shape of the cam 3 is changed at the deformed portion 4. The deformation portion 4 in the first embodiment is formed at the cam bottom 32 in the surface of the cam 3. The broken line S in fig. 3 shows the shape of the cam 3 in a configuration in which the deformed portion 4 is not formed on the surface of the cam 3. The deformed portion 4 is a groove recessed toward the rotation axis of the cam 3 with respect to the shape indicated by the broken line S. The deformation portion 4 extends in the direction of the rotational axis of the cam 3. Details of the deformation portion 4 will be described below.

As shown in fig. 1 and 4, a roller 5 is provided on the surface of the cam 3. The roller 5 has a cylindrical shape and is in contact with the surface of the cam 3. The roller 5 is rotatable about the axis of the roller 5. The shoe 6 is disposed on the opposite side of the cam 3 with respect to the roller 5. The shoe 6 includes a sliding contact surface 61 on a side closer to the roller 5. The sliding contact surface 61 has a circular arc shape. The radius of curvature of the sliding contact surface 61 formed on the shoe portion 6 is equal to or slightly larger than the radius of the roller 5. The sliding contact surface 61 of the shoe 6 is in contact with and slides on the surface of the roller 5 on the side opposite to the cam 3. The shoe 6 is fitted to the inside of the tappet 9.

The tappet 9 includes a hole portion 91 that is in contact with the inner wall 221 of the sliding chamber 22 and slides on the inner wall 221 of the sliding chamber 22, and a protruding portion 92 that protrudes from the inner wall of the hole portion 91 to the inside of the sliding chamber 22. The tappet 9 is in contact with the inner wall 221 of the sliding chamber 22 and slides on the inner wall 221 of the sliding chamber 22 and is configured to reciprocate in the axial direction of the sliding chamber 22. The shoe 6 is disposed inside a hole portion 91 included in the tappet 9 and abuts against the surface of the projection 92 on the side closer to the cam 3. Thus, the roller 5 and the shoe 6 reciprocate in the sliding chamber 22 together with the tappet 9 in the axial direction of the sliding chamber 22 by the rotation of the cam 3.

As shown in fig. 1, a spring seat 93 is placed on the projection 92 of the tappet 9 on the side opposite to the cam 3. The end portion 71 of the plunger 7 is attached to a spring seat 93. A cylinder chamber 80 located inside the cylinder 8 accommodates the plunger 7 so that the plunger 7 can move forward and backward.

The cylinder 8 houses the plunger 7 and is fixed to an end portion 82 that is a part of the housing 2 and forms the slide chamber 22. The cylinder 8 closes the slide chamber 22 on the side opposite to the cam chamber 21. The surface 83 of the cylinder 8 closes the sliding chamber 22. A spring 94 is disposed between surface 83 and spring seat 93. The spring 94 is a compression coil spring and biases the tappet 9, the shoe 6, and the roller 5 toward the cam 3 through the spring seat 93. Therefore, when the cam 3 rotates, the roller 5, the shoe 6, the tappet 9, the spring seat 93, and the plunger 7 reciprocate in the axial direction of the slide chamber 22.

The pump chamber 81 is formed at a deep portion of the cylinder chamber 80, and the cylinder chamber 80 accommodates the plunger 7 in the cylinder 8. The pump chamber 81 is located in the cylinder chamber 80 on the side opposite to the cam 3. Fig. 1 shows a state in which the cam top 31 is positioned on the axis of the plunger 7. In this state, the volume of the pump chamber 81 is minimum. When the cam rotates from the state shown in fig. 1, the plunger 7 moves toward the cam 3. When the cam base 32 is positioned on the axis of the plunger 7, not shown, the volume of the pump chamber 81 is maximized. Hereinafter, the position of the plunger 7 in a state where the volume of the pump chamber 81 is minimum is referred to as a top dead center. On the other hand, hereinafter, the position of the plunger 7 in a state where the volume of the pump chamber 81 is maximum is referred to as a bottom dead center.

Fuel is supplied to the pump chamber 81 of the cylinder 8 through the metering valve unit 10 and is discharged from the pump chamber 81 of the cylinder 8 through the discharge valve unit 15. The metering valve unit 10 includes a metering valve 11 and an electromagnetic drive module 12. The metering valve 11 is an on/off valve and is configured to communicate a fuel supply passage 13, through which fuel is supplied from a fuel inlet port, not shown, to the pump chamber 81 or to block the fuel supply passage 13 from the pump chamber 81. The electromagnetic drive module 12 is configured to control a driving operation of the metering valve 11 by energization corresponding to control implemented by an Electronic Control Unit (ECU) not shown.

The discharge valve unit 15 includes a discharge valve 16, a discharge spring 17, a fixing member 18, and the like, and is provided in a discharge passage 19 configured to communicate to the pump chamber 81. The discharge valve 16 is a poppet valve and can be seated on or lifted from a valve seat provided on the inner wall of the discharge passage 19. The discharge spring 17 biases the discharge valve 16 toward the valve seat. The fixing member 18 fixes the discharge spring 17 in the discharge passage 19.

The operation of the fuel injection pump 1 will be described below. The fuel injection pump 1 pressurizes and supplies fuel through a process including an intake stroke, a metering stroke, a compression stroke, and an exhaust stroke.

In the intake stroke, the plunger 7 moves from the top dead center to the bottom dead center, and the volume of the pump chamber 81 increases. Therefore, the fuel pressure in the pump chamber 81 is reduced. At this time, the metering valve 11 is opened, and the fuel supply passage 13 communicates to the pump chamber 81. Therefore, the fuel is drawn into the pump chamber 81 from the fuel supply passage 13.

In the metering stroke, the plunger 7 moves from the bottom dead center to the top dead center. During this state, the metering valve 11 remains in its open state. Therefore, the fuel returns from the pump chamber 81 to the fuel supply passage 13. The metering valve 11 controls the amount of fuel discharged from the discharge passage 19 in a discharge stroke after a compression stroke in a metering stroke. When the metering valve 11 is closed in the movement of the plunger 7 from the bottom dead center to the top dead center, the communication between the fuel supply passage 46 and the pump chamber 81 is cut off. Thus, the metering stroke ends and the process shifts to the compression stroke.

In the compression stroke, after the metering stroke, the plunger 7 is further moved toward the top dead center. The decrease in the volume of pump chamber 81 raises the pressure of the fuel in pump chamber 81 and causes compression of the fuel.

In the discharge stroke, when the force received by the discharge valve 16 from the fuel in the pump chamber 81 during the compression stroke becomes larger than the sum of the force received by the discharge valve 16 from the fuel downstream of the discharge valve 16 and the biasing force of the discharge spring 17, the discharge valve 16 is lifted from the valve seat. Therefore, the fuel that has been compressed in the pump chamber 81 is discharged from the discharge passage 19.

Subsequently, when the plunger 7 starts moving from the top dead center to the bottom dead center, the discharge valve 16 is closed, and the metering valve 11 is opened. Thus, the suction stroke is performed again. That is, the fuel injection pump 1 pressurizes and supplies fuel by repeating an intake stroke, a metering stroke, a compression stroke, and a discharge stroke.

The function of the deformation portion 4 provided in the cam 3 of the fuel injection pump 1 will be described below. When the cam 3 starts rotating, for example, when the internal combustion engine is started or the motor is started, the operation of the fuel injection pump 1 is started in a state where there is no oil film between the shoe 6 and the roller 5 and the friction coefficient between the shoe 6 and the roller 5 is high. Therefore, the roller 5 may not rotate about the axis of the roller 5, and the cam 3 and the roller 5 may be in a sliding state in which the cam 3 and the roller 5 slide each other.

In addition, when the friction coefficient between the shoe 6 and the roller 5 increases, for example, due to clogging with foreign matter between the shoe 6 and the roller 5 while the fuel injection pump 1 is driven, the roller 5 may not rotate about the axis of the roller 5, and the cam 3 and the roller 5 may be in a sliding state. In this way, in the case where the circumferential speed of the cam 3 is increased while the cam 3 and the roller 5 continue to be in the sliding state, the cam 3 and the roller 5 may exceed the biting limit and may be damaged.

In this state, the braking force, hereinafter referred to as shoe braking torque, by which the shoe 6 brakes the rotation of the roller 5 is larger than the force, hereinafter referred to as cam driving torque, by which the cam 3 drives the roller 5 to rotate. Therefore, the cam 3 and the roller 5 are in a sliding state. That is, when the shoe braking torque is larger than the cam driving torque, the roller 5 does not rotate. The shoe braking torque can be reduced by reducing the coefficient of friction between the shoe 6 and the roller 5. In general, the coefficient of friction between the shoe 6 and the roller 5 can be reduced by reducing the surface roughness of the shoe 6. However, the method of reducing the surface roughness of the shoe 6 has process limitations and requires advanced configurations to be more effective. In addition, advanced methods may not increase manufacturing costs.

In the first embodiment, effective lubrication between the shoe 6 and the roller 5, i.e., formation of an oil film between the shoe 6 and the roller 5, reduces the coefficient of friction between the shoe 6 and the roller 5. More specifically, the fuel injection pump 1 includes a deformation portion 4 provided on a part of the surface of the cam 3. The surface shape of the cam 3 changes at the deformation portion 4. The deformation portion 4 in the first embodiment is a groove formed on a part of the surface of the cam 3 and has a shape different from a cam profile that contributes to pressurizing and supplying fuel by the fuel injection pump 1. The groove extends in the direction of the axis of rotation of the cam 3. The depth of the groove of the deformation portion 4 hardly affects the pressurization and supply of the fuel by the fuel injection pump 1. In addition, the deformation portion 4 in the first embodiment is placed at the cam bottom 32 in the surface of the cam 3. The cam 3 in the first embodiment includes two cam ridges, and the cam bottom 32 is formed at two positions on the surface of the cam 3 over the entire circumference of the cam 3. The deforming portions 4 are provided on the two cam bottoms 32, respectively.

Fig. 5A to 5D are explanatory diagrams showing a state in which the cam 3 and the roller 5 in the sliding state are shifted to a rolling state in which the cam 3 and the roller 5 roll on each other. The dashed line with the reference number 23 in fig. 5A to 5C shows the axis of the sliding chamber 22. The dashed lines with the reference N in fig. 5A and 5C show the common normal between the cam 3 and the roller 5.θ in fig. 5A to 5C shows an angle of a common normal line between the cam 3 and the roller 5 with respect to the axis of the sliding chamber 22, that is, θ shows a pressure angle. A state in which the pressure angle θ is located on the front side in the rotational direction of the cam 3 with respect to the axis of the slide chamber 22 is hereinafter referred to as a state in which the pressure angle θ is located on the + side ((positive) side). On the other hand, a state in which the angle θ is located rearward in the rotational direction of the cam 3 with respect to the axis of the slide chamber 22 is hereinafter referred to as a state in which the pressure angle θ is on the minus side (minus side).

The cam 3 starts rotating at an arbitrary position when the internal combustion engine starts its operation, when the electric motor starts its operation, or the like. Fig. 5A shows a state immediately before the position where the roller 5 contacts the cam 3 reaches the deforming portion 4 after the cam 3 starts rotating. At this time, the friction coefficient between the shoe 6 and the roller 5 is high, and there is no oil film between the shoe 6 and the roller 5. Therefore, the roller 5 is not rotated, and the roller 5 or the shoe 6 is not in a sliding state. The roller 5 and the cam 3 are in a sliding state. At this time, the pressure angle θ is on the negative side.

Fig. 5B shows a state in which the roller 5 is in contact with the cam 3 at the center of the deformed portion 4 after the cam 3 is slightly rotated from the state shown in fig. 5A. At this time, the pressure angle θ is equal to 0 °. Further, fig. 5C shows a state in which the roller 5 is in contact with the cam 3 at the rear in the direction of the rotational direction of the cam 3 after the cam 3 is slightly rotated from a state in which the roller 5 is in contact with the cam 3 at the center of the deformed portion 4 as shown in fig. 5B. At this time, the pressure angle θ is on the positive side.

As shown in fig. 5A to 5C, when the position where the roller 5 contacts the cam 3 moves in the deformation portion 4, the pressure angle θ greatly changes in a short time. Therefore, the center position of the roller 5 is greatly moved in a short time. When the moving speed of the roller 5 is greater than the speed of discharging oil between the shoe 6 and the roller 5, the oil between the shoe 6 and the roller 5 is pressed, and pressure is generated in the oil due to the pressing effect. Thus, an oil film is formed and held between the shoe 6 and the roller 5. In fig. 5C and 5D, the hatched portion with the mark OF shows an oil film formed and maintained between the shoe 6 and the roller 5. When the oil film is formed and held between the shoe 6 and the roller 5 as described above, the friction coefficient between the shoe 6 and the roller 5 is reduced. Therefore, the shoe braking torque becomes smaller than the cam driving torque, and the roller 5 and the shoe 6 are in the slipping state, while the cam 3 and the roller 5 are in the rolling state.

Subsequently, as shown in fig. 5D, an oil film is held between the shoe 6 and the roller 5. Thus, the sliding state of the roller 5 and the shoe 6 and the rolling state of the cam 3 and the roller 5 are maintained. I.e. the cam 3 and the roller 5 are protected from seizure.

In the first embodiment, the deformation portion 4 is formed at the cam bottom 32 in the surface of the cam 3. When the roller 5 moves on the surface of the cam 3, the rate of change of the pressure angle θ is highest at the cam bottom 32 in the cam profile that contributes to the pressurization and supply of the fuel. Therefore, the deformation portion 4 placed at the cam bottom portion 32 makes the rate of change of the pressure angle θ high. That is, by increasing the moving speed of the center position of the roller 5 when the roller 5 moves on the deformed portion 4 formed in the surface of the cam 3, an oil film is stably formed and held between the shoe 6 and the roller 5, thereby stably bringing the cam 3 and the roller 5 into a rolling state.

The radius of curvature r of the deformation 4 will be described below with reference to fig. 6 and 7. Fig. 6 shows an example in the case where the radius of curvature r of the deformed portion 4 is large. On the other hand, fig. 7 shows an example in the case where the radius of curvature r of the deformed portion 4 is small. Fig. 6 and 7 show a state where the roller 5 passes over the deforming portion 4. An arrow M in fig. 6 and 7 shows a direction in which the roller 5 moves on the deformation portion 4 provided on the cam 3 when the roller 5 moves on the deformation portion 4 with the cam 3 rotating.

When the radius of curvature r of the deformed portion 4 is large as shown in fig. 6, the rate of change of the pressure angle θ on the roller 5 moving on the deformed portion 4 is small as compared with the case shown in fig. 7. That is, the squeezing effect obtained by the deformation portion 4 is small. On the other hand, when the radius of curvature r of the deformed portion 4 is small as shown in fig. 7, the rate of change in the pressure angle θ on the roller 5 moving on the deformed portion 4 is large as compared with the case shown in fig. 6. That is, the squeezing effect obtained by the deformation portion 4 is large. Therefore, the radius R of curvature of the deformed portion 4 can be approximated to the radius R of the roller 5 within a manufacturable range. More specifically, the relationship between the radius R of curvature of the deformation portion 4 and the radius R of the roller 5 may be set in a range of R < R × 30. More specifically, the relationship between the radius R of curvature of the deformation portion 4 and the radius R of the roller 5 may be set in a range of R < R × 10. In other words, as the radius of curvature R of the deformed portion 4 is closer to the radius R of the roller 5, the squeezing effect obtained by the deformed portion 4 becomes larger. That is, forming and maintaining an oil film between the shoe 6 and the roller 5 by a squeezing effect enables the cam 3 and the roller 5 to be stably in a rolling state.

The fuel injection pump 1 in the first embodiment described above produces the effects described below.

(1) The fuel injection pump 1 in the first embodiment includes a deformation portion 4 that is provided on a part of the surface of the cam 3 and has a shape different from a cam profile that contributes to pressurization and supply of fuel. The deformation portion 4 is a groove extending in the rotational axis direction of the cam 3. According to this configuration, when the roller 5 moves on the deformation 4 formed in the surface of the cam 3 by the rotation of the cam 3, an oil film is formed and held between the shoe 6 and the roller 5 by the squeezing effect and the friction coefficient between the shoe 6 and the roller 5 is reduced. Therefore, the shoe braking torque becomes smaller than the cam driving torque. That is, the roller 5 and the shoe 6 are in a sliding state, and the cam 3 and the roller 5 are in a rolling state. Therefore, the injection pump 1 can protect the cam 3 and the roller 5 from being stuck and improve reliability.

(2) In the deformed portion 4 of the first embodiment, the rate of change of the pressure angle θ in the state where the roller 5 moves on the deformed portion 4 formed in the surface of the cam 3 is larger than the rate of change of the pressure angle θ in the state where the roller 5 moves on a portion of the surface of the cam 3 other than the deformed portion 4. Therefore, the moving speed of the center position of the roller 5 moving on the deformed portion 4 formed in the surface of the cam 3 is larger than the moving speed of the center position of the roller 5 moving on the portion of the surface of the cam 3 other than the deformed portion 4. The oil between the shoe 6 and the roller 5 is pressed and a pressure is generated on the oil by the pressing effect. Thus, an oil film is formed and held between the shoe 6 and the roller 5.

(3) In the first embodiment, the deformation portion 4 is located at the cam base portion 32. Therefore, when the roller 5 moves on the surface of the cam 3, the rate of change of the pressure angle θ at the cam bottom 32 is largest in the cam profile. That is, the deformation portion 4 provided on the cam bottom portion 32 makes the rate of change of the pressure angle θ large. By increasing the moving speed of the center position of the roller 5 that moves on the deformation 4 formed in the surface of the cam 3, the formation and retention of the oil film between the shoe 6 and the roller 5 are stably achieved, and the cam 3 and the roller 5 are enabled to be stably in the rolling state.

(4) In the first embodiment, the deformation portions 4 are provided at the respective two cam bottoms 32. That is, the rolling state of the cam 3 and the roller 5 makes it possible to protect the cam 3 and the roller 5 from seizure at an early stage after the cam 3 starts rotating (for example, when the internal combustion engine is started or the electric motor is started).

(5) In the first embodiment, the relationship between the radius of curvature R of the deforming portion 4 and the radius R of the roller 5 is set to the range of R < R × 30. That is, by reducing the radius of curvature r of the deformed portion 4 within the manufacturable range, the rate of change of the pressure angle θ when the roller 5 moves on the deformed portion 4 can be made large. Therefore, the cam 3 and the roller 5 can be made to roll stably by increasing the moving speed of the center position of the roller 5 moving on the deforming part 4 and by forming and maintaining an oil film between the shoe 6 and the roller 5 by utilizing the squeezing effect.

(6) In the first embodiment, the deformed portions 4 are provided on the respective two cam bottoms 32 in the surface of the cam 3. That is, when the cam 3 starts rotating, for example, when the internal combustion engine is started or the electric motor is started, the roller 5 moves on the deformed portion 4 formed in the surface of the cam 3 during one reciprocation of the plunger 7 in the cylinder 8. Therefore, the rolling state of the cam 3 and the roller 5 in the early state after the cam 3 starts rotating makes it possible to protect the cam 3 and the roller 5 from seizure.

(second embodiment to fourth embodiment)

The fuel injection pumps 1 of the second to fourth embodiments are different from the first embodiment only in the structure of the deformation portion 4. Only the structure different from the first embodiment will be described below. The cam 3 provided in the fuel injection pump 1 of the second to fourth embodiments includes two cam ridges, similarly to the first embodiment. Fig. 8 to 10 will be referred to in the second to fourth embodiments and show only the cam 3 provided in the fuel injection pump 1.

(second embodiment)

A second embodiment will be described below with reference to fig. 8. As described in the first embodiment, the fuel injection pump 1 pressurizes and supplies fuel through a process including an intake stroke, a metering stroke, a compression stroke, and an exhaust stroke. In the intake stroke, the plunger 7 moves from the top dead center to the bottom dead center. Therefore, the roller 5 is in contact with the surface of the cam 3 in a region placed rearward in the direction of the rotational direction of the cam 3 from the predetermined cam top portion 31 to the cam bottom portion 32 in the suction stroke. Hereinafter, a region where the roller 5 contacts the surface of the cam 3 in the suction stroke is referred to as "a region contributing to the suction stroke in the cam surface". The double arrow a in fig. 8 shows the area of the cam surface that contributes to the intake stroke.

The deformation portion 4 in the second embodiment is formed in a region of the cam surface that contributes to the suction stroke. In the second embodiment, three deformation portions 4 are continuously formed in the cam surface in the region that contributes to the suction stroke in the circumferential direction. The deformation portion 4 in the second embodiment is a groove recessed toward the rotational axis of the cam 3. The groove extends in the direction of the axis of rotation of the cam 3.

The cam 3 in the second embodiment includes two cam ridges and forms regions in the cam surface that contribute to the intake stroke at two locations on the surface of the cam 3 over the entire circumference of the cam 3. The areas of the cam surface that contribute to the intake stroke at the two positions each comprise three deformations 4. That is, the deforming portions 4 are provided on the two cam ridges, respectively.

The effects of the fuel injection pump 1 in the above-described second embodiment will be described below. During the pressurization and supply of the fuel by the fuel injection pump 1, the fuel pressure in the pump chamber 81 rises in the compression stroke and the discharge stroke. The force that the plunger 7 receives from the fuel pressure in the pump chamber 81 is transmitted to the roller 5 through the plunger 7 and the shoe 6. Therefore, the pressure applied to the position where the roller 5 contacts the cam 3 is increased. On the other hand, during the pressurization and supply of the fuel by the fuel injection pump, the fuel pressure in the pump chamber 81 becomes negative in the intake stroke. Therefore, the pressure applied to the position where the roller 5 contacts the cam 3 is smaller than the pressure applied during the compression stroke and the discharge stroke. That is, in the second embodiment, by forming the deformed portion 4 in the area of the cam surface that contributes to the suction stroke, the load applied to the deformed portion 4 and the roller 5 when the roller 5 moves on the deformed portion 4 is reduced, thereby protecting the roller 5 from seizure.

In the second embodiment, the plurality of cam ridges respectively include the deformed portions 4. That is, when the cam 3 starts rotating in a state where, for example, the internal combustion engine is started or the electric motor is started, the roller 5 moves on the deformed portion 4 formed in the surface of the cam 3 during one reciprocation of the plunger 7 in the cylinder 8. Therefore, the rolling state of the cam 3 and the roller 5 in the early state after the cam 3 starts rotating makes it possible to protect the cam 3 and the roller 5 from seizure.

(third embodiment)

A third embodiment will be described below with reference to fig. 9. As described in the first embodiment, when the fuel is pressurized and supplied by the fuel injection pump 1, the plunger 7 moves from the bottom dead center to the top dead center during the metering stroke, the compression stroke, and the exhaust stroke. Thus, in the metering stroke, the compression stroke, and the discharge stroke, the roller 5 is in contact with the surface of the cam 3 in the region where the cycle of the cam 3 is placed forward between the specific cam bottom 32 and the cam top 31. Hereinafter, the region where the roller 5 contacts the surface of the cam 3 in the metering stroke, the compression stroke, and the discharge stroke is referred to as "a region in the cam surface contributing to the metering stroke to the discharge stroke". The double-headed arrows β in fig. 9 each show a region of the cam surface that contributes to the metering stroke to the discharge stroke. The double-headed arrows α in fig. 9 each show a region on the cam surface contributing to the intake stroke, similarly to the double-headed arrows α in fig. 8.

The deformation portion 4 in the third embodiment is formed in a region of the cam surface that contributes to the intake stroke and a region of the cam surface that contributes to the metering stroke to the discharge stroke. In the third embodiment, the five deformation portions 4 are formed continuously in the circumferential direction from the region of the cam surface that contributes to the intake stroke to the region of the cam surface that contributes to the metering stroke to the discharge stroke. The deformation portion 4 in the third embodiment is a groove recessed toward the rotational axis of the cam 3. The groove extends in the direction of the axis of rotation of the cam 3.

The cam 3 in the third embodiment includes two cam ridges and forms regions contributing to the suction stroke in the cam surface at two positions on the surface of the cam 3 over the entire circumference of the cam 3. In addition, over the entire circumference of the cam 3, regions of the cam surface that contribute to the metering stroke to the discharge stroke are also formed at two locations on the surface of the cam 3. The deformation 4 is provided on a region of the cam surface which contributes to the intake stroke and a region of the cam surface which contributes to the metering stroke to the discharge stroke. That is, the deformation portions 4 are provided on the two cam ridges, respectively.

In the fuel injection pump 1 of the third embodiment described above, the rolling state of the cam 3 and the roller 5 at an early stage after the cam 3 starts rotating, for example, when the internal combustion engine is started or the electric motor is started, makes it possible to protect the cam 3 and the roller 5 from seizure.

(fourth embodiment)

The fourth embodiment will be described below with reference to fig. 10. The deformation portion 4 in the fourth embodiment is a protrusion formed on a part of the surface of the cam 3 and has a shape different from the cam profile that contributes to pressurizing and supplying the fuel by the fuel injection pump 1. The protruding portion protrudes outward in the radial direction of the cam 3 and extends in the direction of the rotational axis of the cam 3. The height of the protruding portion is set so as to hardly affect the pressurization and supply of the fuel by the fuel injection pump 1.

The deformation portion 4 in the fourth embodiment is formed in the cam base 32 in the surface of the cam 3. The cam 3 in the fourth embodiment includes two cam ridges, and therefore, the cam bottom 32 is formed at two positions on the surface of the cam 3 over the entire circumference of the cam 3. The deforming portions 4 are provided on the two cam bottoms 32, respectively. The structure in the fourth embodiment described below also produces the same operational effects as the first embodiment and the like. In addition, the structure in which the deformation portion 4 is a protrusion portion according to the fourth embodiment can also be applied to the second embodiment, the third embodiment, the fifth embodiment or the sixth embodiment which will be described below.

(fifth and sixth embodiments)

The fuel injection pumps 1 according to the fifth embodiment and the sixth embodiment are different from the fuel injection pumps according to the first embodiment and the like only in the configuration of the cam 3, and the others are similar to the first embodiment. Therefore, a configuration different from that in the first embodiment and the like will be described below. Fig. 11 according to the fifth embodiment and fig. 12 according to the sixth embodiment show only the cam 3 provided in the fuel injection pump 1.

(fifth embodiment)

As shown in fig. 11, the cam 3 provided in the fuel injection pump 1 of the fifth embodiment includes four cam ridges. The deformation portion 4 in the fifth embodiment is a groove recessed toward the rotational axis of the cam 3. The groove extends in the direction of the axis of rotation of the cam 3.

The cam 3 in the fifth embodiment includes four cam ridges, and the regions contributing to the suction stroke in the cam surface are formed at four positions on the surface of the cam 3 over the entire circumference of the cam 3. The regions of the cam surface at the four positions that contribute to the intake stroke each include one deformation 4. That is, the deformation portions 4 are formed in the plurality of cam ridges, respectively. The deformation portion 4 may be placed at any position on the surface of the cam and is not limited to the position shown in fig. 11.

(sixth embodiment)

The cam 3 provided in the fuel injection pump 1 in the sixth embodiment includes three cam ridges. The deformation portion 4 in the sixth embodiment is a groove recessed toward the rotational axis of the cam 3. The groove extends in the direction of the axis of rotation of the cam 3.

The cam 3 in the sixth embodiment includes three cam ridges and the cam bottom 32 is formed at three positions on the surface of the cam 3 over the entire circumference of the cam 3. The cam base 32 at the three positions includes one deformation portion 4 each. The deformation portion 4 may be placed at any position on the cam surface and is not limited to the position shown in fig. 12.

(other embodiments)

The present disclosure is not limited to the above embodiments and/or modifications, but may be further modified in various ways without departing from the spirit of the present disclosure. Each embodiment in the present disclosure is not independent of each other and may be combined as appropriate, except where combination is obviously not possible. The elements provided to the embodiments are not essential to each embodiment except in the case where each element is specified as a particularly essential element or where such elements are clearly essential in principle. In addition, even in the case where a number such as an amount, a value, a number, a range is mentioned in each embodiment, the present disclosure is not limited to a specific number unless when the number is specified as being particularly necessary or when the number is obviously limited to a specific number in principle. In addition, even in the case where a specific shape, a specific positional relationship, or the like is mentioned in each embodiment, the present disclosure is not limited to the specific shape, the specific positional relationship, or the like unless the specific positional relationship or the like is specifically specified or the specific shape, the specific positional relationship, or the like is explicitly limited in principle.

(1) In each embodiment, it is described that the fuel injection pump 1 pressurizes and supplies fuel, such as light oil, which is injected and supplied to the internal combustion engine. However, the present disclosure is not limited to the above. The fuel injection pump 1 can pressurize and supply fuel injected to, for example, a discharge pipe or an intake pipe. Further, the fuel injection pump 1 may pressurize and supply fuel injected to a gasoline engine or fuel injected to a fuel cell.

(2) In each embodiment, the cam 3 provided in the fuel injection pump 1 includes a plurality of cam ridges. However, the present disclosure is not limited to the above. The cam 3 provided in the fuel injection pump 1 may include a cam ridge.

(3) The deformation 4 is formed in the surface of the cam 3 at the cam bottom 32, in a region of the cam surface contributing to the intake stroke, or in a region contributing to the metering stroke to the discharge stroke. However, the present disclosure is not limited to the above. The deformation 4 may be formed, for example, at a base circle in the surface of the cam top 31 or the cam 3.