JP2000145573A - Fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce gear chattering noise of a gear train by forming, on a cam, a protrude for canceling a torque in a positive direction applied on a camshaft by pushing a plunger by a return spring, in a pump wherein a plunger is protruded up against the return spring by the cam and fuel is forcibly supplied. SOLUTION: In a gear train for driving a camshaft 29 of a fuel injection pump, gear chattering noise is not generated since a working face of each gear 71 to 74 for forming the gear train is not changed in the case where the camshaft 29 is driven by a crankshaft 70 at all times. When rotating speed of the crankshaft 70 is fluctuated, rotating speed of the camshaft 29 is accelerated, the working face is inversed, and gear chattering noise is generated. For solving a speed difference between both the shafts 29 and 70, a protrude 78 is formed in an initial region of a part 77 of rising gradient in a cam 30. It is thus possible to effectively reduce gear chattering noise and noise in association with the gear chattering noise without exerting wrong effect on a fuel injection operation.

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, and more particularly to a fuel injection pump in which a plunger is pushed up by a cam provided on a camshaft against a return spring to feed fuel.

[0002]

2. Description of the Related Art A diesel engine is provided with a fuel injection pump. The fuel is intermittently pumped by the fuel injection pump, and the fuel is pumped from the fuel injection pump in synchronization with the piston in the cylinder almost reaching the top dead center. The fuel is injected into the cylinder from the injection port on the tip side of the fuel injection nozzle. The fuel spray injected from the fuel injection nozzle is
When the piston moves to the top dead center side, it is spontaneously ignited by the heat of the compressed air, the combustion causes gas expansion, and the gas expansion moves the piston to the bottom dead center side to generate output. I have.

An in-line fuel injection pump used in such a diesel engine has plunger pump units as many as the number of cylinders, and the plungers of these plunger pump units are sequentially protruded by a cam mounted on a cam shaft. It can be raised,
Thus, the fuel is pumped at a predetermined timing. Here, the camshaft of the fuel injection pump is driven by a drive gear mounted on the crankshaft of the engine via an idle gear, and is カ ム of the rotation speed of the crankshaft.
It is designed to be driven at a rotational speed of.

[0004]

As described above, the fuel injection pump attached to the diesel engine is driven by the drive gear provided on the crankshaft of the engine via the idle gear. Here, each plunger of the fuel injection pump is provided with a return spring, and such a return spring presses the plunger against the cam. Therefore, the cam pushes up the plunger against the return spring.

[0005] By the action of the return spring of the plunger of such a fuel injection pump, the camshaft intermittently receives a torque in the positive direction, that is, a torque that causes the camshaft to rotate forward. In this case, because the camshaft rotates in the forward direction at a speed faster than the crankshaft,
When the engine is driving the camshaft, the contact surface of the gear is reversed. Thereafter, when the state changes to a normal state, that is, a state in which the engine drives the camshaft, the contact surface of the gear returns to the original state.

[0006] The change in the contact surface of the gear due to the reversal of the torque between the camshaft of the fuel injection pump and the crankshaft of the engine causes the rattling noise. That is, if the cam of the fuel injection pump is driven by the gear provided on the camshaft via the idle gear, the gears in this gear train generate rattling noise, thereby generating noise.

Conventionally, measures have been taken to reduce such rattling noise, such as using a scissors gear, or selecting a gear to reduce backlash.
However, the use of scissor gears increases costs. In addition, the method of reducing backlash by selecting gears has a problem that the number of guaranteed man-hours is increased, productivity is reduced, and ultimately the cost is increased.

On the other hand, in order to reduce the amount of nitrogen oxides contained in the exhaust gas of a diesel engine, the injection timing of a fuel injection pump tends to be delayed. However, there is a problem that such a delay in injection timing causes an increase in noise caused by rattle of a gear train between the camshaft of the fuel injection pump and the engine.

The present invention has been made in view of such a problem, and more effectively reduces the gear rattle of the gear train when driving the camshaft of the fuel injection pump via the gear train. An object of the present invention is to provide a fuel injection pump configured as described above.

[0010]

According to a first aspect of the present invention, there is provided a fuel injection pump in which a plunger is pushed up against a return spring by a cam provided on a camshaft to feed fuel under pressure. A projection formed on the cam to cancel the forward torque applied to the camshaft when the plunger is pressed by the cam.

According to a second aspect of the present invention, there is provided a fuel injection pump in which a plunger is pushed up by a cam provided on a camshaft against a return spring to feed fuel.
The present invention relates to a fuel injection pump, wherein a projection for applying a load to the camshaft is formed in a portion of an initial profile of an upward slope of the cam.

According to a third aspect of the present invention, there is provided a fuel injection pump in which a plunger is pushed up by a cam provided on a cam shaft against a return spring to feed fuel under pressure.
The present invention relates to a fuel injection pump, wherein a protrusion having a substantially constant lift is formed in a portion of a profile of a downward slope of the cam.

A preferred embodiment of the present invention is a gear train for driving the fuel injection pump without affecting the performance of the fuel injection pump and the engine by changing the cam profile provided on the camshaft of the fuel injection pump. The noise associated with the rattling noise is reduced.

In particular, a projection is formed in the initial region of the upward slope of the cam profile to form a cam profile which advances this region. A load is applied to the camshaft by such a cam profile, and a torque in the forward direction is applied. I try to negate it. Alternatively, a protruding portion where the lift does not substantially change is formed at a position corresponding to 60 ° before the top dead center in the middle of the downward slope of the cam profile to apply a negative torque to the camshaft, Thus, the rattling noise is reduced by offsetting the torque in the positive direction.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel injection nozzle 20 for injecting fuel into a cylinder of an engine is connected to a corresponding pump unit 26 of a fuel injection pump 25 by an injection pipe 24 as shown in FIG. The fuel injection pump 25 has a mechanical governor 27, and the control rack 28 is moved by the mechanical governor 27 to adjust the supply amount of fuel injected at one time. The fuel injection pump 25 has a camshaft 29, and a cam 30 attached to the camshaft 29 drives each pump unit 26. A timer 31 is provided on the camshaft 29.
1 adjusts the injection timing.

The fuel injection nozzle 20 is, as shown in FIG.
The tip is formed of a nozzle body 34, and a plurality of injection holes 35 are formed at the tip of the nozzle body 34. The nozzle body 34 is attached to a nozzle holder 37 by a retainer 36. A nozzle needle 38 is slidably held in the nozzle body 34.
The upper end of the nozzle needle 38 is
, The compression coil spring 40 in the nozzle holder 37 is pressed downward. As a result, the nozzle needle 38 is pressed against the valve seat 41 formed on the nozzle body 34 to shut off fuel. Further, a fuel passage 42 communicating with the injection pipe 24 is formed in the nozzle holder 37. The fuel passage 42 communicates with a fuel passage 43 of the nozzle body 34. A fuel reservoir 51 is formed at the end of the fuel passage 43.

The upper end of the spring 40 pressing the pressing rod 39 is received by a spring receiver 44. An adjusting screw 45 is attached to the upper end of the spring receiver 44. The adjusting screw 45 is screwed with a female screw 46 formed on the inner peripheral surface of the nozzle holder 37. A protrusion 48 is formed on the side surface of the nozzle holder 37, and a male screw 49 is formed on the protrusion 48, and a connection nut 50 screwed with the male screw 49.
Thereby, the injection pipe 24 is connected to the nozzle holder 37.

Next, the structure of each pump unit of the fuel injection pump 25 will be described. As shown in FIG. 2, a tappet 55 is attached to the lower end of the plunger 54.
The tappet 55 is pressed downward by a compression coil spring 56 constituting a return spring, and is thereby pressed against the outer peripheral surface of the cam 30. A spill port 58 is formed in a barrel 57 in which the plunger 54 is slidably fitted.
An inclined groove 59 is formed in the outer peripheral surface of the plunger 54 so as to substantially face the plunger 54.

On the outer peripheral side of the barrel 57, a pinion 60 is rotatably supported. A control sleeve 61 is fixed to the pinion 60 and a notch 62 formed in the control sleeve 61.
Receives the engagement plate 63. This engagement plate 63 is fixed to the plunger 54.

A delivery valve 64 is provided at the outlet side of each pump unit 26, and is provided on a valve seat 66 provided at a lower portion of the casing 65.
The delivery valve 64 is pressed toward the valve seat 66 by the coil spring 67.

Next, an outline of the operation of the fuel injection device having the above configuration will be described.

The timer 31 depends on part of the engine output.
When the camshaft 29 is driven through the camshaft 29, the cam 30 shaped as shown in FIG. 2 pushes up the roller of the tappet 55, whereby the plunger 54 moves in the barrel 57 against the coil spring 56. Move upward. Then, the top surface of the plunger 54 closes the spill port 58 and starts pumping the fuel. When the plunger 54 moves further upward, the inclined groove 59 eventually aligns with the spill port 58, whereby the pressure in the space above the plunger 54 escapes to the spill port 58 through the inclined groove 59, and the fuel is pumped. finish.

The mechanical governor 2 of the fuel injection pump 25
7 moves the control rack 28, the pinion 60 is rotated, thereby causing the control sleeve 6 to move.
1 will be rotated. The rotation of the control sleeve 61 is transmitted to the plunger 54 through the notch 62 and the engagement plate 63, and the plunger 54 is rotated in the barrel 57. Therefore spill port 5
The effective stroke determined by the position of the inclined groove 59 aligned with the position 8 changes, and the fuel is metered.
The supply amount of fuel injected at one time is controlled. The phase angle of the camshaft 29 is controlled by a timer 31 provided on the camshaft 29 of the fuel injection pump 25, so that the timing of fuel injection is adjusted.

When the plunger 54 feeds the fuel in the barrel 57, the delivery valve 64 is opened, and the fuel is fed to the fuel injection nozzle 20 through the injection pipe 24. The fuel passage 4 of the fuel injection nozzle 20 shown in FIG.
When fuel pressure is applied to the sump 51 through 2 and 43, the nozzle needle 38 is moved
As a result, the nozzle needle 38 moves upward while compressing 0, so that the tip side portion of the nozzle needle 38 is separated from the valve seat 41, and fuel is injected through the injection port 35. When the pumping of the fuel is completed, the nozzle needle 38 is pressed downward via the rod 39 by the elastic restoring force of the spring 40, and its tip is pressed against the valve seat 41 to stop fuel injection.

The fuel is sprayed on the nozzle 3 of the fuel injection nozzle 20.
From 5 onward, the fuel is injected toward the combustion chamber formed on the top surface of the piston in the cylinder of the engine. The fuel spray is spontaneously ignited by the heat of the compressed intake air, combustion occurs in the cylinder, the piston is pushed downward, and the output of the engine is obtained. Thereafter, the exhaust valve is opened, and exhaust gas is discharged through the exhaust port.

Next, a description will be given of a structure for reducing noise caused by rattle when driving the fuel injection pump 25. As shown in FIG. 3, a drive gear 71 is fixed to a crankshaft 70 of the engine. The drive gear 71 meshes with an idle gear 72 and an idle gear 73 coaxial with the idle gear 72.
Are engaged with the driven gear 74. The driven gear 74 is a camshaft 2 of the fuel injection pump 25.
9 is fixed to the tip.

In such a gear train for driving the camshaft 29 of the fuel injection pump 25, when the crankshaft 70 always drives the camshaft 29,
The contact surfaces of the gears 71 to 74 constituting these gear trains do not change, and therefore, no noise accompanying the rattling noise is generated. However, in practice, the rotational speed of the crankshaft 70 of the engine fluctuates as shown in FIG. 4, and the camshaft 29 receives a forward torque by the return spring 56 which pushes down the plunger 54.
Due to these factors, even if instantaneous, the rotation speed of the camshaft 29 exceeds the rotation speed of the crankshaft 70, whereby the contact surface is inverted and rattling noise is generated.

This operation will be described in more detail. Here, the mechanism of the gear rattle noise generation will be described, limited to the drive system between the crankshaft 70 and the fuel injection pump 29. As shown in FIG. 4, the rotational speed of the crankshaft 70 is the slowest at an angle corresponding to the top dead center of each cylinder, and the fastest at a position corresponding to the bottom dead center. In the case of a six-cylinder engine, a sine-curve-shaped speed fluctuation of a 120 ° cycle is produced such that three peaks are generated in one revolution of the engine.

FIG. 5 shows the first cylinder 60 before top dead center.
The rotation speed A of the crankshaft 70 from 0 ° to the top dead center and the rotation speed B of the camshaft 29 of the fuel injection pump 25 in this section are shown. The camshaft 29 of the fuel injection pump 25 has the slowest speed near the top dead center of the engine for fuel injection by the fuel injection nozzle 20 and has six cams 30 provided on the same camshaft 29. Determines the rotational speed B of the camshaft 29.

As shown in FIG. 5, when the rotational speeds of the first cylinder are measured in a section from 60 ° before the top dead center to the top dead center, the crankshaft 70 is in a compression process of the first cylinder. And the camshaft 29 of the fuel injection pump 25 is not as slow as the crankshaft 70, resulting in a speed difference BA between them.
Due to such a speed difference BA, a gap is generated in any meshing of the gear train from the drive gear 71 to the driven gear 74. After that, when the speed of the camshaft 29 sharply decreases due to the fuel injection near the top dead center, the speed A of the crankshaft 70 follows the speed B of the camshaft 29, and the gap between the gears is reduced. At this time, rattling noise is generated.

Therefore, in order to eliminate such rattling noise, the speed A of the crankshaft 70 and the camshaft 29
The speed difference B-A with the speed B may be eliminated. In other words, it is only necessary to prevent the speed of the camshaft 29 of the fuel injection pump 25 from being higher than the crankshaft 70 near 60 ° before the top dead center and the speed difference BA being generated.

In the vicinity of 60 ° before the top dead center, a forward direction force is applied to the camshaft 29 by the return spring 56 for returning the plunger 54 to the camshaft 29, so that a torque as shown by C in the graph of FIG. 5 is generated. Will be. Therefore, it is sufficient to reduce the force in the forward direction by generating a reaction force opposing the force in the forward direction. That is, the torque of the camshaft 29 may be changed from C to D in the graph of FIG. For this purpose, a force acting in the negative rotation direction against the return spring 56 may be generated. That is, the rising position of the cam profile of the cam 30 may be advanced forward so that the cam lift in FIG.

As shown in FIGS. 6 and 7, this can be achieved by forming a projection 78 shown in FIG. 7, especially in the initial region of the upwardly inclined portion 77 of the cam 30, thereby affecting the fuel injection. It is possible to effectively eliminate the noise caused by the rattle without giving any noise.

Next, a second embodiment will be described. This second embodiment is shown in FIG. 8, and FIGS. 1 to 6 used for the description of the first embodiment are used for the description.

The gear train shown in FIG. 3 is used to drive the camshaft 29 of the fuel injection pump 25 by the engine. That is, the crank gear 71 is
Driven gear 7 of fuel injection pump 25 via
4 is driven. Briefly describing the behavior of each of the gears 71 to 74, in the case of an in-line six-cylinder engine, the crankshaft 70 fluctuates at approximately 60 ° intervals as shown in FIG. As the speed decreases, the speed becomes highest before and after the bottom dead center rotated by 60 °. On the other hand, as shown in FIG. 5, the gear of the fuel injection pump 25 does not readily decrease in speed while the crankshaft 70 gradually decreases from the maximum speed at 60 ° before the top dead center, as shown in FIG. As a result, the speed difference BA is generated, and a gap is generated between the teeth of the gear trains 71 to 74. Then, near the top dead center, as shown in FIG. 5, when the gear 74 of the fuel injection pump 25 suddenly slows down for fuel injection, the crankshaft 70 catches up and generates rattling noise.

The rotation speed of the camshaft 29 of the fuel injection pump 25 is determined by the shape of the cam 30 shown in FIG. At 60 ° before the top dead center of the first cylinder, the speed B of the fuel injection pump 29 is determined by the profile of a plurality of cams provided on the camshaft 29. That is, the cam 30 corresponding to the first cylinder is in contact with the base circle, and the other cams 30 are in contact with the downward slope.

At this time, the torque generated in the fuel injection pump 25 is as shown in FIG. Therefore, the fuel injection pump 25 does not decelerate and the camshaft 2
Nine is faster. In order to prevent noise caused by rattling noise, it is only necessary to take measures to prevent such a reversal of the speed and to make the rotation speed of the camshaft 29 of the fuel injection pump 25 slower than that of the crankshaft 70.

As a countermeasure, it is sufficient to prevent the camshaft 29 of the fuel injection pump 25 from generating a forward rotation torque. That is, a portion where the lift does not change may be formed in the cam profile 30 in the middle of the downward slope near −60 °. Therefore, as shown in FIG. 8, three protruding portions 80 are formed at intervals of about 60 ° in the downwardly inclined portion 79 of the cam 30. In such a protrusion 80, the plunger 5
4 is maintained at a substantially constant value. That is, these projections 80 generate a force that cancels the downward pressing force of the return spring 56, thereby preventing the camshaft 29 from generating torque in the forward direction.

As shown in FIG.
When the cam 30 is formed so as to form the three projections 80, the gear 74 of the fuel injection pump 25 is reduced near 60 ° before the top dead center of the first cylinder, and the idle gears 72, 73 The tooth surfaces are not separated from each other, and no rattling noise is generated. Therefore, the down slope 7 of the cam 30 is thus
By forming a portion 80 in which the lift does not change in a portion 9 to generate a forward torque on the camshaft 29, the forward torque of the camshaft 29 is reduced and the gear for driving the fuel injection pump is reduced. Row rattle can be reduced. In the configuration shown in FIG. 8, three projections 80 are formed on the downwardly inclined portion 79. However, three projections are not necessarily required, and one or two projections 80 may be formed. You may.

[0040]

According to the first aspect of the present invention, a projection is formed on the cam such that the plunger is pushed by the return spring to cancel the forward torque applied to the camshaft.

Therefore, the torque in the forward direction is canceled out by such a protrusion, so that the camshaft does not rotate at a higher rotation speed than the drive side, and the noise caused by the rattling noise is suppressed.

According to a second aspect of the present invention, a protruding portion for applying a load to the camshaft is formed in a portion of an initial profile of an ascending slope of the cam.

Thus, the cam is loaded by the projections formed in the portion of the initial profile of the upward slope of the cam, so that the projections cause the portion of the initial profile of the upward slope to have a load. The rotation speed of the camshaft is prevented from becoming higher than that on the drive side, thereby reducing noise caused by rattle.

According to a third aspect of the present invention, a protrusion having a substantially constant lift is formed at a portion of the cam having a downward slope profile.

Therefore, it is possible to apply a load to the camshaft by such a protrusion having a substantially constant lift, thereby reducing the rotational speed of the portion where the camshaft is faster than the drive side, and Of the gear train for driving the camshaft can be suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a fuel injection nozzle connected to a fuel injection pump.

FIG. 2 is a perspective view of a main part of the fuel injection pump.

FIG. 3 is a front view of a gear train that drives a camshaft of the fuel injection pump.

FIG. 4 is a graph showing a change in rotation speed of a crankshaft of an engine.

FIG. 5 is a graph showing a rotation speed, a torque generated in a cam, and a lift of the cam.

FIG. 6 is a front view of a cam provided on a cam shaft.

FIG. 7 is a front view of a single cam.

FIG. 8 is a front view of a cam according to another embodiment.

[Explanation of symbols]

 Reference Signs List 20 fuel injection nozzle 24 injection pipe 25 fuel injection pump 26 pump unit 27 mechanical governor 28 control rack 29 cam shaft 30 cam 31 timer 34 nozzle body 35 injection port 36 retainer 37 nozzle holder 38 nozzle needle 39 pressing rod 40 spring 41 valve seat 42, 43 fuel passage 44 spring receiver 45 adjusting screw 46 female screw 47 cap 48 protrusion 49 male screw 50 connection nut 51 fuel reservoir 54 plunger 55 tappet 56 coil spring (return spring) 57 barrel 58 spill port 59 inclined groove 60 pinion 61 control sleeve 62 Notch 63 Engagement plate 64 Delivery valve 65 Casing 66 Valve seat 67 Coil spring 70 Crankshaft 71 Drive gear 72 Idle Gear 73 Idle gear 74 Driven gear 77 Uphill section 78 Projection 79 Downhill section 80 Projection

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigekatsu Inagaki 3-1-1, Hinodai, Hino-shi, Tokyo Inside Hino Motors Industry Co., Ltd. (72) Yasuo Miura 3-1-1, Hinodai, Hino-shi, Tokyo 1-Hino Motor Co., Ltd. (72) Inventor Toshiyoshi Nakamura 3-1-1, Hinodai, Hino-shi, Tokyo F-term within Hino Motor Co., Ltd. CC26 CC34 CE04 CE34

Claims (3)

[Claims] 1. A fuel injection pump in which a plunger is pushed up by a cam provided on a camshaft against a return spring to feed fuel by pressure, wherein the plunger is pushed by the return spring and the camshaft is pushed. A fuel injection pump, wherein a projection is formed on the cam so as to cancel a forward torque applied to the cam. 2. A fuel injection pump in which a plunger is pushed up by a cam provided on a camshaft against a return spring to feed fuel under pressure, wherein said cam has an initial profile of an upward slope. A fuel injection pump having a projection for applying a load to a camshaft. 3. A fuel injection pump in which a plunger is pushed up against a return spring by a cam provided on a camshaft to feed fuel under pressure. A fuel injection pump having a constant projection.