JP2002349388A - Fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection pump capable of reducing the noise of an engine by reducing that which occurs at driving of a plunger. SOLUTION: In the fuel injection pump which drives the plunger through a tappet by a cam circularly mounted on a camshaft to pump a fuel, the camshaft is rotatably supported in a housing 10 through a ball bearing 18 and slide bearing 19, and the drive of the plunger by the cam is performed in such a state that the tappet is slidable vertically in a tappet guide cylinder 31. In this case, the ratio of a tappet diameter to the inner diameter of the tappet guide cylinder is set within a range of 0.996±0.001.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for driving a plunger by a cam to pump fuel.
In particular, the present invention relates to measures for reducing noise generated when the plunger is driven.

[0002]

2. Description of the Related Art Conventionally, this type of fuel injection pump has a plunger reciprocally driven in the axial direction via a tappet by a cam provided around a cam shaft which is rotated by the driving force of an engine. The pressurized fuel is pressure-fed via a communication passage to a distribution shaft that rotates in synchronization with the camshaft by a driven gear that meshes with a bevel gear mechanism drive gear that is rotatably connected to the camshaft, The distribution shaft supplies the fuel to the fuel injection valve corresponding to each convex portion of the cam through the distribution valve corresponding to each convex portion of the cam. In this case, the tappet drives the plunger by the cam in the tappet guide cylinder, and a spring for holding the tappet in contact with the cam is provided in the tappet guide cylinder. Even if the tappet is driven in a direction away from the axis of the cam, the tappet is urged to return to the axis of the cam by a spring force.

The cam shaft is rotatably supported on one side and the other side of the cam by a fuel injection pump housing via bearings.

[0004]

However, in the above-mentioned conventional fuel injection pump, one side and the other side of the camshaft are supported via bearings, respectively. There is a problem that noise is generated when the plunger driven by the contact is driven.

The noise is attributed to the contact between the cam and the tappet. The contact may cause the camshaft to bend or the tappet to cause poor sliding in the tappet guide cylinder. Have been. That is, the vibration due to the camshaft bending and the poor sliding of the tappet is transmitted to the fuel injection pump housing, and the surface of the fuel injection pump housing is vibrated to generate noise. Therefore, as the amount of camshaft deflection or tappet sliding failure increases, the amount of vibration on the surface of the fuel injection pump housing also increases, thereby increasing noise, making it impossible to reduce engine noise.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel injection pump capable of reducing noise generated when a plunger is driven to reduce engine noise. To provide.

[0007]

Means for Solving the Problems To achieve the above object, a solution taken by the invention according to claim 1 is to drive a plunger via a tappet by a cam provided around a cam shaft to supply fuel. Assume a fuel injection pump for pumping. The camshaft is rotatably supported on the fuel injection pump housing via a bearing. Furthermore, the diameter of the camshaft in the range from the cam to the bearing is increased so as to be substantially the same as the cam reference circle diameter closest to the camshaft.

According to this specific matter, the second moment of area of the camshaft in the range from the cam to the bearing is increased,
The bending rigidity of the camshaft is increased. Therefore, the amount of deflection of the camshaft due to the contact between the cam and the tappet when the plunger is driven is reduced, and the amount of vibration of the fuel injection pump housing surface due to the deflection of the camshaft is reduced, thereby reducing noise. This makes it possible to reduce the noise of the engine.

On the other hand, when the cam shaft is rotatably supported via bearings at positions adjacent to the cam on both sides of the cam with respect to the fuel injection pump housing, as in the second aspect, The camshaft is supported from both sides (one side and the other side) in the immediate vicinity where the cam and the tappet abut when the plunger is driven, and the location where the camshaft bends is suppressed to a short distance between the support points near the tappet. Will be. For this reason, the amount of deflection of the camshaft is suppressed small, and the amount of vibration of the fuel injection pump housing surface due to the deflection of the camshaft is suppressed, thereby reducing noise, thereby making it possible to reduce engine noise. .

Further, the tappet is driven by a plunger by a cam in the tappet guide cylinder, and the ratio of the diameter of the tappet to the inner diameter of the tappet guide cylinder is 0.996 ± 0. When the value is set within the range of 0.001, the gap between the tappet and the tappet guide cylinder is set to an appropriate value that allows an appropriate oil film to be formed on the inner peripheral surface of the tappet guide cylinder. When the cam and the tappet come into contact with each other when the plunger is driven, poor sliding of the tappet, specifically, the impact of the tappet swinging and colliding with the inner peripheral surface of the tappet guide cylinder is reduced. For this reason, the tappet collision noise on the inner peripheral surface of the tappet guide cylinder is suppressed to a small level, and the vibration amount of the fuel injection pump housing surface due to the poor tappet sliding is suppressed, so that noise is reduced. Noise can be reduced.

The camshaft is rotatably supported on the fuel injection pump housing via a separate bearing member, and a cushioning member is provided between the fuel injection pump housing and the bearing member. In this case, the vibration of the camshaft caused by the contact between the cam and the tappet when the plunger is driven is absorbed by the cushioning member, and the vibration of the camshaft is transmitted to the surface of the fuel injection pump housing. Reduced noise,
The noise of the engine can be reduced.

Further, according to the fifth aspect, the shape change rate in the rotation direction from the cam reference circle closest to the cam shaft of the cam to the top of the cam farthest from the cam shaft to the farthest from the cam shaft is:
When the cam is formed so that the shape change rate in the rotation direction from the cam top to the cam reference circle is small, the tappet is compared with the process in which the tappet is most separated from the axis of the cam by the cam top. The process of returning from the top of the cam to the cam reference circle closest to the axis of the cam becomes gentle, and the impact caused by the contact between the cam and the tappet when the tappet returns is reduced. Therefore, the amount of vibration of the surface of the fuel injection pump housing caused by the contact between the cam and the tappet is suppressed, and the noise is reduced, whereby the noise of the engine can be reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
Front partial cross-sectional view of a fuel injection pump according to the embodiment,
2 is a partial cross-sectional view of the same side, and FIG. 3 is a partial cross-sectional view of the same plane.

1 to 3, the configuration of the fuel injection pump 1 will be described.

A housing 10 as a fuel injection pump housing has a camshaft 2 in the front-rear direction (in FIG.
Are rotatably inserted, and the cam shaft 2 is provided with a cam 21.
Are arranged to rotate integrally. The cam 21 of the camshaft 2
The front part (the left part in FIG. 2) is the housing 1
0 is rotatably supported by a ball bearing 18 as a bearing via a bevel gear 54 (described later). A portion (right side portion in FIG. 2) of the camshaft 2 behind the cam 21 is rotated by a slide bearing 19 as a bearing with respect to a separate bearing housing 10b as a bearing member fixed to the housing 10. It is freely supported.

Further, the tappet 3 is in contact with the cam 21, and the plunger 4 is disposed above the tappet 3. The plunger 4 includes the upper housing 1
The fuel introduced into the plunger barrel 41 is inserted into the plunger barrel 41 mounted in the vertical direction at 0 a, and is fed to the distribution shaft 5 by pressure. A spill ring 42 and a control sleeve 43 are inserted into the plunger 4. The control sleeve 43 is connected to a rack 44, and the slide of the rack 44 causes the control sleeve 43 to rotate with respect to the plunger 4. The rack 44
Is connected to a governor mechanism (not shown), and is slid by the governor mechanism in accordance with the operation state of the engine.

The distribution shaft 5 is vertically disposed on the upper housing 10a and the housing 10, and a distribution drive shaft 51 is connected to a lower portion of the distribution shaft 5. A bevel gear 52 is provided at a lower end of the distribution drive shaft 51. An oil pump 5 is provided at the center of the distribution drive shaft 51.
3 is provided, and the fuel is supplied to the plunger 4 with the rotation of the distribution drive shaft 51.
A bevel gear 52 mounted on the lower end of the distribution drive shaft 51 meshes with a bevel gear 54 that is inserted and fixed to the cam shaft 2 so as to be relatively non-rotatable. Thus, the distribution shaft 5 is driven. An oil seal 55 is mounted on the distribution drive shaft 51 so that fuel does not enter the portions where the bevel gears 52 and 54 are disposed. The fuel pumped by the plunger 4 is supplied to the upper part of the distribution shaft 5, and the fuel is supplied from the distribution shaft 5 to the delivery valve 11 via the high-pressure oil passage 56.

A lever 42a is engaged with the spill ring 42, and the lever 42a is
2 is rotated. The timer lever mechanism 12 is disposed vertically across the upper housing 10a and the housing 10, and is engaged with the lever 42a at a lower portion of the timer lever mechanism 12. As a result, the vertical position of the spill ring 42 in the plunger 4 changes, and the timing for starting the fuel pumping by the plunger 4 is adjusted.

Next, the overall configuration of the distribution type fuel injection pump will be described.

As shown in FIG. 4, a cam 21 is
Are provided integrally with each other, and a tappet 3 is disposed above the camshaft 2. A plunger 4 disposed in the vertical direction is connected to the tappet 3, and is urged downward by a spring 40 attached to a lower portion of the plunger 4. The tappet 3 comes into contact with the cam 21 by the rotation of the camshaft 2 and slides up and down. The plunger 4 slides up and down as the tappet 3 slides up and down. ing. The plunger 4 is configured to be inserted into the fuel gallery 13. The fuel is introduced from the fuel gallery 13 into a fuel chamber (not shown), and the fuel is pressure-fed to the distribution shaft 5.

Fuel is pumped from the fuel tank 15 to the fuel gallery 13 through a feed pump 15a, a filter 15b, a low-pressure fuel gallery 15c, and an oil pump 53. A control sleeve 43 and a spill ring 42 are inserted into the plunger 4. The control sleeve 43 is inserted into the plunger 4 so as not to rotate relatively, and is connected to the rack 16 that slides by a governor mechanism (not shown). The sliding of the rack 16 causes the plunger 4 to rotate together with the control sleeve 43, and the amount of fuel supplied by the plunger 4 changes. The spill ring 42 is connected to the timer lever mechanism 12 as described above, and is configured to adjust the fuel injection timing by sliding up and down on the side surface of the plunger 4 by the timer lever mechanism 12. Timer lever mechanism 12
Is composed of a lever 42a, a timer piston (not shown), and a spring for urging the timer piston downward, and the piston slides with a change in the fuel pressure in the fuel gallery 13. When the piston slides, lever 4
The spill ring 42 is configured to slide through the 2a.

The fuel gallery 13 includes the accumulator 1
The fuel gallery 13 is configured to prevent excessive pressure from being applied to the fuel gallery 13 and the drain 3a. A pressure regulating valve 53a is connected to the oil supply pump 53, and excess fuel is discharged from the pressure regulating valve 53a to the low-pressure fuel gallery 15c. The oil feed pump 53 is driven by a distribution drive shaft 51 connected to the distribution shaft 5, and a bevel gear 52 is fixed to a lower end of the distribution shaft drive shaft 51. The bevel gear 52 is a camshaft 2
Meshed with a bevel gear 54 fixed to the cam shaft 2
The distribution shaft 5 is rotated together with the distribution shaft drive shaft 51 via the bevel gear 54 and the bevel gear 52 by the rotation of.

A delivery valve 11 is connected to the distribution shaft 5 by an oil passage. A nozzle 57 for injecting fuel into each combustion chamber of the engine is connected to the delivery valve 11 through a high-pressure oil passage 56, and the fuel is pumped through the high-pressure oil passage 56, and the fuel is injected from the nozzle 57 into the combustion chamber of the engine. Fuel is injected.

The part where the low-pressure fuel gallery 15c, the bevel gear 54 and the bevel gear 52 are disposed is an oil seal 5
5 to prevent fuel from entering the portion where the bevel gear 54 and the bevel gear 52 are disposed. That is, the distribution shaft drive shaft 51 connected to the distribution shaft 5
An oil seal 55 is inserted into a lower portion of the low pressure fuel gallery 15c. The oil seal 55 is disposed between the side surface of the distribution drive shaft 51 and the housing of the bevel gear 54 and the bevel gear 52 (not shown). On the other hand, the arrangement of the bevel gear 54 and the bevel gear 52 is sealed.

Next, the structure of fuel supply and discharge of the fuel injection pump 1 provided in the upper housing 10a will be described.

First, the configuration of the fuel gallery 13 and the oil feed pump 53 will be described with reference to FIG.

The oil supply pump 53 is disposed on the upper part of the housing 10, and a cover 53 is provided on the upper part of the oil supply pump 53.
b is fixed. When the upper housing 10a is assembled to the housing 10, a portion corresponding to the vicinity of the oil supply pump 53 and a lower portion of the upper housing 10a corresponding to the vicinity of the plunger barrel 41 are formed in a concave shape.
The concave portion is used as the fuel gallery 13. That is, the lower part of the upper housing 10a is formed in the fuel gallery 13, and the oil feed pump 53 is disposed immediately below the fuel gallery 13.

Next, the distribution shaft 5 and the distribution shaft sleeve 5b
The configuration of the suction / discharge path in the above will be described.

A distribution shaft sleeve 5 b is mounted outside the distribution shaft 5, and a lower portion of the distribution shaft sleeve 5 b projects into the fuel gallery 13. In the lower part of the distribution shaft sleeve 5b, a reverse suction path 5c for performing reverse suction of fuel corresponding to each cylinder is provided radially from the inside. Although four reverse suction paths 5c are provided in the present embodiment, as many reverse suction paths 5c as necessary are provided.
c can be configured. The distribution shaft sleeve 5b is fixed to the upper housing 10a, and the distribution shaft 5 is rotatably inserted into the distribution shaft sleeve 5b. The distribution shaft 5 is connected to a distribution shaft drive shaft 51, and is configured to rotate as the cam shaft 2 rotates. The distribution axis 5
Is provided with a groove 45a which is connected to a fuel pressure sending high pressure path 5f (described later) communicating with the fuel chamber 45.
A vertical groove-shaped distribution groove 45b is formed below 5a.
As shown in FIG. 6, when the distribution groove 45b coincides with the reverse suction path 5c, the fuel in the fuel gallery 13 can flow into the fuel chamber 45 via the reverse suction path 5c, the distribution groove 45b and the groove 45a. It is configured. In the above configuration, when the plunger 4 slides downward, the reverse suction path 5c coincides with the distribution groove 45b.

Further, referring to FIG.
A fuel pressure feeding high pressure path 5f, a fuel discharge path 5d, and a reverse suction path 5c are formed in order from the top in FIG. 2b. The fuel discharge path 5d is provided above the reverse suction path 5c, and is connected to an oil path 11a communicating with the delivery valve 11. The oil passage 11a linearly connects the delivery valve 11 and the outer end of the fuel discharge passage 5d, and the connection angle between the oil passage 11a, the delivery valve 11 and the fuel discharge passage 5d is formed to be obtuse.

A high-pressure fuel supply passage 5f is formed above the fuel discharge passage 5d. The high-pressure fuel supply passage 5f is connected to an oil passage 41c formed in the upper housing 28a.
Is connected to the oil passage 41b of the plunger barrel 41. The fuel pressure-fed to the plunger 4 via the oil passage 41b, the oil passage 41c and the fuel pressure high-pressure passage 5f reaches the groove 45a of the distribution shaft 5, and the above-mentioned vertical groove-shaped distribution groove formed on the distribution shaft 5. 45b smoothly flows down to the fuel discharge path 5d below the oil path 11b as described above.
Through the delivery valve 11. Further, excess fuel flows down the reverse suction path 5c further below the distribution groove 45b via the distribution groove 45b, and returns to the fuel gallery 13 as described above.

The configuration of the distribution shaft 9 will be described in more detail.

As described above, on the side surface of the distribution shaft 5, the vertical distribution groove 45b is provided in the vertical direction.
5b is a groove 45a provided on the upper side peripheral surface of the distribution shaft 5.
Connected to The groove 45a is formed at a position connected to the high-pressure fuel supply passage 5f of the distribution shaft sleeve 5b, and the fuel flows into the groove 45a from the high-pressure fuel supply passage 5f. The lower part of the distribution groove 45b is configured to be wide, and the wide part is connected to the fuel discharge path 5d. A slit 5a is provided on the side surface of the distribution shaft 5, and the slit 5a is provided on the oil passage 5b and the shaft center which are perpendicular to the axial direction from the slit 5a and are drilled to the shaft center position. The connected oil passage 5c is connected. The oil passage 5c connects the slit 5a and the upper surface of the distribution shaft 5 via the oil passage 5b.
The fuel flowing from the slit 5a can be introduced into a fuel reservoir 50 provided above the distribution shaft 5. The slit 5a is connected to the fuel discharge path 5d, and is formed to have a minimum necessary size to allow fuel to flow from the fuel discharge path 5d. When the pressurized fuel remains in the oil passage 11a and the fuel discharge passage 5d, the distribution shaft 5 rotates,
By connecting the slit 5a to the fuel discharge path 5d, fuel flows into the slit 5a via the fuel discharge path 5d. The fuel flowing into the slit 5a is supplied to the oil passage 5c.
The fuel is discharged to the fuel reservoir 50 above the distribution shaft 5 via. Thereby, the pressure in the oil passage 11a and the fuel discharge passage 5d can be reduced.

Next, the structure of the upper part of the upper housing 10a will be described.

A distribution shaft sleeve 5b and a plunger barrel 41 are fixed to the upper housing 10a. The upper portion of the distribution shaft sleeve 5b is closed by a cap member 46, and the cap member 46 is connected to the distribution shaft sleeve 5b. Is in contact with the upper end of the Also, the upper housing 10
A communication portion 47 is provided near the upper part of the distribution shaft sleeve 5b and the plunger barrel 41 of FIG.
Is formed by a drill hole or the like in the upper housing 10a, and is connected to an overflow orifice 48 arranged on the side of the fuel injection pump 1. Distribution shaft sleeve 5
A gap is provided between b and the upper portion of the plunger barrel 41 with the cap member 46, and the gap is connected to the communication portion 47.

In the above configuration, the distribution shaft sleeve 5b
The fuel can flow into the gap above the plunger barrel 41 from between the distribution shaft 5 and the distribution shaft sleeve 5b, and can flow from between the plunger 4 and the plunger barrel 41. The communicating portion 47 communicates with the fuel gallery 13 and the plunger barrel 41 via the upper gap between the distribution shaft sleeve 5b and the plunger barrel 41. The communication part 47 has an overflow orifice 48.
Connected to the overflow orifice 48
Thus, the air in the fuel injection pump 1 can be removed.

As a characteristic part of the present invention, as shown in FIG.
The plunger 4 is driven by the cam 21 so as to be slidable in the vertical direction.
The diameter of the tappet 3 and the inner peripheral surface 3 of the tappet guide tube 31
The ratio to the diameter of 1a is set in the range of 0.996 ± 0.001.

Thus, in this embodiment, the tappet 3
The gap between the tappet guide tube 31 and the tappet guide tube 31 is set to an appropriate value that allows an appropriate oil film to be formed on the inner peripheral surface 31a of the tappet guide tube 31, and the cam 21 and the tappet 3 when the plunger 4 is driven by this oil film. At the time of contact, poor sliding of the tappet 3, specifically, the impact of the tappet 3 swinging and colliding with the inner peripheral surface 31 a of the tappet guide tube 31 is reduced. For this reason, the inner peripheral surface 31 of the tappet guide tube 31
The noise of the tappet 3 at (a) is suppressed to a small level, the amount of vibration of the surface of the housing 10 due to the poor sliding of the tappet 3 is suppressed, and the noise is reduced, whereby the noise of the engine can be reduced.

<Second Embodiment> Next, a second embodiment of the present invention will be described.
Will be described with reference to FIG.

In this embodiment, the configuration of the cam shaft is changed. The other configuration except for the camshaft is the same as that of the first embodiment.
This is the same as in the case of the embodiment, the same reference numerals are given, and the description is omitted.

That is, in this embodiment, as shown in FIG. 7, the camshaft diameter in the range from the cam 21 of the camshaft 6 to the ball bearing 18 is set to the reference circle diameter m of the cam 21 closest to the camshaft 6. The diameter is enlarged so as to have the same diameter.

Thus, in the present embodiment, the secondary moment of area of the camshaft 6 in the range from the cam 21 to the ball bearing 18 is increased, and the bending rigidity of the camshaft 6 is increased.
For this reason, the amount of deflection of the camshaft 6 due to the contact between the cam 21 and the tappet 3 when the plunger 4 is driven is reduced, and the amount of vibration of the surface of the housing 10 due to the deflection of the camshaft 6 is reduced, thereby reducing noise. Thus, the noise of the engine can be reduced.

In this embodiment, the cam 2 of the cam shaft 6
Although the camshaft diameter in the range from 1 to the ball bearing 18 has been expanded,
The diameter of the camshaft in the range from the cam of the camshaft to the plain bearing may also be enlarged.

<Third Embodiment> Next, a third embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

In this embodiment, the configuration of the cam shaft is changed. The other configuration except for the camshaft is the same as that of the first embodiment.
This is the same as in the case of the embodiment, the same reference numerals are given, and the description is omitted.

That is, in this embodiment, as shown in FIG. 8, the front adjacent position of the cam shaft 7 adjacent to the cam 21 is:
The housing 10 is rotatably supported via a slide bearing 71 as a bearing. That is, the camshaft 7
Are sliding bearings 71, 19 at positions adjacent to the cam adjacent to the housing 10 on both front and rear sides of the cam 21, respectively.
It is rotatably supported via.

Thus, in this embodiment, the camshaft 7
Is a short support point between the front and rear sliding bearings 71 and 19 in the vicinity of the tappet 3 where the cam shaft 7 is bent near the tappet 3 when the cam 21 and the tappet 3 are in contact with each other when the plunger 4 is driven. The distance between them will be reduced. For this reason, the amount of deflection of the camshaft 7 is suppressed to a small value, and the amount of vibration of the surface of the housing 10 due to the deflection of the camshaft 7 is suppressed, thereby reducing noise. As a result, the noise of the engine can be reduced.

In this embodiment, the cam 2 of the cam shaft 7
Although the front adjacent position adjacent to 1 is rotatably supported via the slide bearing 71, the front adjacent position may be rotatably supported by the housing via the ball bearing.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

In this embodiment, the configuration of the bearing housing that supports the camshaft is changed. The other configuration except for the bearing housing is the same as that of the first embodiment, and the same reference numerals are given and the description is omitted.

That is, in this embodiment, as shown in FIG. 9, the bearing housing 10b is attached to the housing 10 via the oil-resistant rubber 8 as a cushioning member. That is, the housing 10 and the bearing housing 10b
And an oil-resistant rubber 8 is interposed therebetween.

Thus, in the present embodiment, when the plunger 4 is driven, the vibration of the cam shaft 2 caused by the contact between the cam 21 and the tappet 3 is absorbed by the buffer member, and the vibration of the cam shaft causes the fuel injection pump housing to move. Vibration transmission to the surface is suppressed and noise is reduced, thereby making it possible to reduce engine noise.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described.
Will be described with reference to FIGS.

In this embodiment, the structure of the cam is changed. The other configuration except for the cam is the same as that of the first embodiment, and the same reference numerals are given and the description is omitted.

That is, in the present embodiment, as shown in FIG. 10, the cam 9 drives the plunger 4 via the tappet 3 by the cam 9 to feed fuel to the three delivery valves 11 for three cylinders. Has been applied to the fuel injection pump. In this case, the cam 9 includes three cam tops 9a.
Is provided.

The cam 9 has a shape change rate in the rotational direction (indicated by an arrow in FIG. 10) from the cam reference circle M closest to the cam shaft 2 to the cam top 9a furthest from the cam shaft 2, and the cam top. The shape change rate in the rotation direction from the portion 9a to the cam reference circle M is reduced. Note that the cam top 9a corresponds to the shape change rate in the rotation direction from the cam reference circle M to each cam top 9a.
The original shape change rate in the rotation direction up to the cam reference circle M is indicated by a broken line in FIG.

In this case, as shown in FIG. 11, the cam lift with respect to the cam angle is greater in the process from each cam top 9a to the cam reference circle M than in the process from the cam reference circle M to each cam top 9a. It has the characteristic of becoming gentler. Further, as shown in FIG. 12, the cam acceleration with respect to the cam angle
The process from the top of each cam 9a to the cam reference circle M is more gradual than the process up to. The original shape change rate in the rotation direction from the cam top circle 9a to the cam reference circle M, which corresponds to the shape change rate in the rotation direction from the cam reference circle M to each cam top 9a, is shown in FIGS. Each is indicated by a broken line.

Thus, in the present embodiment, the tappet 3
Is rotated by the cam top 9a from the cam reference circle M to each cam top 9a.
The process of returning from a to the cam reference circle M becomes gentle, and the impact due to the contact between the cam 9 and the tappet 3 when the tappet 3 returns is reduced. For this reason, the cam 9
The amount of vibration on the surface of the housing 10 caused by the contact between the housing 10 and the tappet 3 is suppressed, so that noise is reduced, whereby the noise of the engine can be reduced.

In this embodiment, the cam 9 applied to the fuel injection pump for three cylinders has been described. However, the cam 9 may be applied to a cam applied to the fuel injection pump for four cylinders. It is not limited.

[0061]

As described above, according to the fuel injection pump of the first aspect of the present invention, the diameter of the cam shaft in the range from the cam to the bearing is increased so as to be substantially the same as the cam reference circle diameter. Therefore, the second moment of area of the camshaft is increased to increase the bending rigidity, and the amount of vibration on the surface of the fuel injection pump housing due to the camshaft flexure when the plunger is driven is reduced to reduce noise and reduce engine noise. be able to.

On the other hand, according to the fuel injection pump of the second aspect, the cam shaft is rotatably supported via bearings at adjacent positions on both sides of the cam, so that the short support point between the two bearings near the tappet is provided. The deflection of the camshaft is suppressed by the distance, the amount of vibration of the surface of the fuel injection pump housing caused by the deflection of the camshaft is suppressed, and the noise is reduced, whereby the noise of the engine can be reduced.

According to the fuel injection pump of the third aspect, the ratio between the diameter of the tappet and the inner diameter of the tappet guide cylinder for storing the tappet is set within the range of 0.996 ± 0.001. , The gap between the tappet and the tappet guide cylinder is set to an appropriate value capable of forming an appropriate oil film to mitigate the poor sliding of the tappet when driving the plunger, and the amount of vibration on the surface of the fuel injection pump housing due to the poor sliding of the tappet , Noise can be reduced, and engine noise can be reduced.

According to the fuel injection pump of the fourth aspect, the buffer member is interposed between the fuel injection pump housing and the separate bearing member, so that the cam and the tappet abut when the plunger is driven. Thus, the vibration of the camshaft caused by the vibration can be absorbed, the transmission of the vibration to the surface of the fuel injection pump housing can be suppressed, the noise can be reduced, and the noise of the engine can be reduced.

Further, according to the fuel injection pump of the fifth aspect, the shape change rate in the rotation direction from the cam top to the cam reference circle is different from the shape change rate in the rotation direction from the cam reference circle to the cam top. By reducing the rate, the process of returning from the top of the plunger cam to the cam reference circle is moderated, the amount of vibration on the surface of the fuel injection pump housing due to the contact between the cam and the tappet is reduced, and noise is reduced. Engine noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a partial front sectional view of a fuel injection pump according to a first embodiment of the present invention.

FIG. 2 is a partial side sectional view of the fuel injection pump.

FIG. 3 is a partial plan sectional view of the fuel injection pump.

FIG. 4 is a schematic view schematically showing a configuration of the fuel injection pump.

FIG. 5 is a partial side sectional view showing the configuration of the upper housing.

FIG. 6 is a plan sectional view showing the configuration of the distribution shaft sleeve.

FIG. 7 is a partial side sectional view of the vicinity of a camshaft of a fuel injection pump according to a second embodiment of the present invention.

FIG. 8 is a partial side sectional view near a camshaft of a fuel injection pump according to a third embodiment of the present invention.

FIG. 9 is a partial side sectional view near a camshaft of a fuel injection pump according to a fourth embodiment of the present invention.

FIG. 10 is a front view of a cam of a fuel injection pump according to a fifth embodiment of the present invention.

FIG. 11 is a characteristic diagram showing characteristics of a cam lift with respect to a cam angle.

FIG. 12 is a characteristic diagram showing characteristics of cam acceleration with respect to a cam angle.

[Explanation of symbols]

Reference Signs List 1 fuel injection pump 10 housing (fuel injection pump housing) 10b bearing housing (bearing member) 18 ball bearing (bearing) 19 slide bearing (bearing) 2 cam shaft 21 cam 3 tappet 4 plunger 71 slide bearing (bearing) 8 oil resistant rubber (Buffer member) 9 cam 9a top of cam M cam reference circle m cam reference circle diameter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F04B 9/04 F04B 9/04 D

Claims (5)

[Claims] 1. A fuel injection pump in which a plunger is driven by a cam provided around a cam shaft via a tappet to feed fuel under pressure, wherein the cam shaft is rotatable via a bearing with respect to a fuel injection pump housing. A fuel injection pump which is supported and is enlarged such that a cam shaft diameter in a range from the cam to the bearing is substantially the same as a cam reference circle diameter closest to the cam shaft. 2. A fuel injection pump for pumping fuel by driving a plunger through a tappet by a cam provided around a cam shaft, wherein the cam shaft is provided on both sides of the cam with respect to a fuel injection pump housing. A fuel injection pump, which is rotatably supported at adjacent positions via bearings. 3. A fuel injection pump for pumping fuel by driving a plunger via a tappet by a cam provided around a camshaft, wherein the tappet drives the plunger by a cam in a tappet guide cylinder. The ratio between the diameter of this tappet and the inner diameter of the tappet guide cylinder is
A fuel injection pump characterized by being set in the range of 0.996 ± 0.001. 4. A fuel injection pump for pumping fuel by driving a plunger via a tappet by a cam provided around a cam shaft, wherein the cam shaft is provided via a separate bearing member with respect to the fuel injection pump housing. A fuel injection pump characterized in that the fuel injection pump is rotatably supported with a buffer member interposed between the fuel injection pump housing and the bearing member. 5. A fuel injection pump for pumping fuel by driving a plunger via a tappet by a cam provided around a camshaft, wherein the cam is more proximate to the camshaft than a cam reference circle closest to the camshaft. A fuel injection pump characterized in that the shape change rate in the rotation direction from the top of the cam to the cam reference circle is smaller than the shape change rate in the rotation direction to the far top of the cam.