JP2003239820A - Distribution type fuel injection pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of a distribution type fuel injection pump wherein a rotational load of a roller ring is increased and an excessive load is applied to a slide pin when fuel injection pressure is enhanced following reinforcement of the regulation of exhaust gas and the slide pin is abnormally worn when it minutely vibrates under conditions of deteriorated fuel lubricity. <P>SOLUTION: The slide pin 52 transmitting movement of a timer piston 51 to the roller ring 8 is formed by aluminium, chromium and molybdenum steel, its strength of an internal structure is enhanced by a quench-and-temper process, and its surface strength is enhanced by nitriding. In such a slide pin 52, internal strength is enhanced and the surface strength is enhanced to 1.5 times of a conventional product. Consequently, even under conditions of deteriorated lubricity due to injection pressure enhancement of fuel and low-sulfurization of the fuel, abnormal wear of the slide pin 52 is suppressed and fatigue breakage is also suppressed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution type fuel injection pump for distributing fuel to a plurality of cylinders of a diesel engine and feeding the fuel under pressure.

[0002]

2. Description of the Related Art A distributed fuel injection pump is equipped with a timer device for mechanically adjusting a fuel injection timing to advance or retard. This timer device changes the rotational position of the roller ring with respect to the face cam to change the timing at which the cam crest rides on and off the roller ring, that is, the timing at which the plunger reciprocates. The structure of the timer device includes a roller ring rotatably supported, a slide pin having one end inserted in the roller ring, and a timer piston having the other end of the slide pin inserted therein. By driving, the rotation position of the roller ring is changed.

[0003]

In recent years, emission regulations for diesel vehicles have been tightened worldwide. Along with this, the injection pressure is increased, and the sulfur content in light oil used as fuel for diesel vehicles tends to be reduced year by year. However, reducing the sulfur content of light oil causes the disadvantage of lowering lubricity at the same time, so the sliding part (the fitting part between the roller ring and the slide pin) of the distributed fuel injection pump that is lubricated with light oil wears out. There is a problem to do.

When the injection pressure is increased, the rotating load of the roller ring becomes large, and therefore, an excessive load acts on the slide pin that rotates the roller ring at the fitting portion with the roller ring. If the lubricity of the fuel deteriorates in such a state, the slide pin will be abnormally worn. As described above, when abnormal wear occurs in the fitting portion of the slide pin, the wear increases the operation error of the timer device, and the advance angle is insufficient to cause insufficient output of the engine and deterioration of exhaust gas. In addition, the abrasion powder may be caught in a sliding portion such as a plunger, which may cause sliding failure or sticking.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to prevent wear of a slide pin even when fuel injection pressure is increased or fuel lubricity is deteriorated. The purpose is to provide a distributed fuel injection pump.

[0006]

[Means for Solving the Problems] [Means for Claim 1] By adopting the means according to claim 1, the surface of the slide pin is subjected to a hardening treatment so as to enhance the wear resistance of the slide pin. Even if the injection pressure is applied or the fuel with low lubricity is used, the wear of the slide pin can be suppressed for a long period of time. In this way, by suppressing the wear of the slide pin, it is possible to suppress the occurrence of an operation error of the timer device, the timer device can accurately rotate the roller ring, and the injection timing can be advanced accurately over a long period of time. The angle side or the retard side can be controlled.

That is, even if the fuel injection pressure is increased or low lubricity fuel is used, the advance control by the timer device can be accurately performed over a long period of time. Therefore, it is possible to prevent the occurrence of engine output shortage due to insufficient advance angle and the deterioration of exhaust gas. Further, since it is possible to suppress the generation of wear powder from the slide pin, it is possible to avoid a problem that the wear powder is caught in a sliding portion such as a plunger and causes poor sliding or sticking.

[Means of Claim 2] By adopting the means of Claim 2 and subjecting the slide pin made of aluminum / chromium / molybdenum steel to nitriding treatment, the surface strength of the slide pin can be increased to a high level. .

[Means of Claim 3] By adopting the means of Claim 3 and coating the slide pin made of chromium molybdenum steel with chromium nitride, the surface strength of the slide pin can be increased to a high level.

[Means of claim 4] By adopting the means of claim 4 and subjecting the slide pin to the quenching treatment and the tempering treatment, the internal structure of the steel constituting the slide pin is improved and the strength is increased. As a result, even if an excessive load is applied to the slide pin for a long period of time, it is possible to avoid the problem of fatigue damage to the slide pin.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to two examples and modifications. [First Embodiment] A first embodiment will be described with reference to FIGS. First, the configuration of the distributed fuel injection pump 1 will be described with reference to FIG.

A distribution type fuel injection pump 1 for pressure-feeding fuel to each cylinder of a diesel engine is provided with a drive shaft 2 that is rotationally driven at a speed that is 1/2 of the crankshaft rotation. Drive shaft 2
A vane type fuel feed pump 3 is provided in the middle of, and the feed pump 3 is rotationally driven as the drive shaft 2 rotates.

A drive gear 5 for driving the governor 4 is attached to the base end side of the drive shaft 2.
The governor 4 will be described later. The drive gear 5 is connected via a coupling 6 so as to rotate integrally with the face cam 7. A roller ring 8 is provided between the drive gear 5 and the face cam 7. A plurality of cam rollers 9 facing the cam crests 7 a of the face cam 7 are attached to the roller ring 8. Cam mountain 7a
The number of cylinders is the same as that of diesel engine cylinders.

A plunger 10 for fuel pressurization is engaged with the face cam 7 via a pin 11 so as to rotate integrally. The plunger 10 is pressed against the face cam 7 by the plunger spring 12 and the lower seat 13, and reciprocates integrally with the face cam 7.

The coupling 6 will be described with reference to FIG. Rotation transmission shaft 7b provided on the face cam 7
Is inserted into a coupling plate 6a attached to the drive shaft 2, and the face cam 7 rotates integrally with the drive shaft 2. That is, the rotational force of the drive shaft 2 is transmitted to the face cam 7 via the coupling plate 6 a and the rotation transmission shaft 7 b, so that the face cam 7 rotates while engaging with the cam roller 9.

As a result, when the face cam 7 is rotated and reciprocated in the left-right direction in the figure by the same number as the number of cylinders,
Along with this, the plunger 10 is reciprocally driven in the same direction while rotating. That is, the plunger 10 is moved forward (lifted up) while the cam crest 7a rides on the cam roller 9 of the roller ring 8, and conversely, the plunger 10 is moved back (during the process that the cam crest 7a rides on the cam roller 9 of the roller ring 8). Lifted down).

The pump housing 14 includes a plunger 1
A cylinder 15 arranged with 0 inserted is provided. The tip surface of the plunger 10 and the cylinder 1
The space between the head plug 16 and the head plug 16 forming the bottom surface of the high pressure chamber 1
It is 7. As many suction grooves 18 as the number of cylinders are formed on the outer peripheral surface of the plunger 10 on the front end side. The suction groove 18 communicates with the pump chamber 20 through a suction port 19 formed in the pump housing 14 when the plunger 10 moves back and the high pressure chamber 17 is depressurized, and the fuel in the pump chamber 20 is discharged. It is for leading to the high pressure chamber 17. A distribution port 22 for guiding the compressed fuel to a discharge port 21 formed in the pump housing 14 is formed inside the tip end side of the plunger 10.
The discharge ports 21 are also opened in the cylinder 15 at equal intervals by the number of cylinders of the diesel engine.

A delivery valve 23 is arranged at the outlet of the discharge port 21. This delivery valve 23
Is for preventing the backflow of the fuel pressure-fed from the discharge port 21, and opens the valve when a certain constant fuel pressure is reached, so that the high-pressure fuel pressure-fed to the discharge port 21 is supplied to the external fuel pressure piping. It discharges from (not shown) toward a fuel injection nozzle (not shown).

An inlet (not shown) communicating with a fuel tank (not shown) is attached to the pump housing 14. This inlet communicates with the suction side of the feed pump 3 via the introduction port 24. The introduction port 24 also communicates with a timer low pressure chamber 26 of a timer device 25 described later.

Inside the pump housing 14, there is formed a pump chamber 20 which receives fuel from the feed pump 3. The pump chamber 20 is the high pressure chamber 17 described above.
The fuel to be sucked in is stored in the plunger 10,
The mechanical sliding portion such as the cylinder 15 is filled with fuel.

The feed pump 3 is the drive shaft 2
When driven by the rotation of the fuel tank, the fuel is introduced from the fuel tank through the inlet into the introduction port 24 and sucked into the feed pump 3. The fuel sucked into the feed pump 3 is pressure-fed to an outlet port (not shown) formed in the pump housing 14 and supplied to the pump chamber 20.

Here, in the suction stroke in which the plunger 10 is returned and the high pressure chamber 17 is depressurized, one of the suction grooves 18 formed on the outer periphery of the tip of the plunger 10 communicates with the pump chamber 20 via the suction port 19. Then, the fuel in the pump chamber 20 is sucked into the high pressure chamber 17. On the contrary, in the compression stroke in which the plunger 10 moves forward to pressurize the high pressure chamber 17,
The high-pressure fuel that has been pressurized by is pressure-fed to a fuel injection nozzle (not shown) through a discharge port 21, a delivery valve 23, and a fuel pressure-feeding pipe (not shown), and the pressure of the pressure-fed fuel becomes the nozzle opening pressure. When it reaches, the fuel injection nozzle injects fuel into the cylinder.

The pump housing 14 is provided with an electromagnetic opening / closing valve 27 for opening and closing the above-mentioned intake port 19 to perform fuel cut or the like. This solenoid valve 27
Is a normally open valve, which opens the intake port 19 in the non-energized (OFF) state and closes the intake port 19 when the coil is energized (ON) to supply fuel to the high pressure chamber 17. Shut off.

On the other hand, the plunger 10 is formed with a spill port 31 having one end communicating with the distribution port 22 and spilling the high-pressure fuel compressed in the high-pressure chamber 17 into the pump chamber 20. The other end of the spill port 31 is connected to the pump chamber 20.
It opens inside, and around the plunger 10,
A spill ring 32 that opens and closes the spill port 31 is externally fitted. The spill ring 32 is slidably fitted around the plunger 10, and is set at a position corresponding to a turning position of a control lever 34 described later. As is clear from the fact that the fuel injection ends when the spill port 31 is exposed from the spill ring 32, the fuel injection amount increases when the spill port 31 is moved to the right side in FIG. 3, and conversely when the spill port 31 is moved to the left side. Is reduced.

The spill ring 32 is set by the turning position of the control lever 34 of the lever assembly 33. The lever assembly 33 is a guide lever 3 whose rotational position is set with respect to the pump housing 14.
5, and a tension lever 37 and a control lever 34, which are rotatably attached via a support shaft 36 of the guide lever 35, are major components.

The control lever 34 is in contact with the tension lever 37 via a start spring 38. The start spring 38 bends and rotates about the support shaft 36 together with the tension lever 37 except when the engine is started. . The lower end of the control lever 34 is engaged with the spill ring 32, and the control lever 3
4 is rotated counterclockwise in FIG. 3, the spill ring 32 is rotated.
Moves to the right and the fuel injection amount increases. Conversely, when the control lever 34 is rotated rightward in FIG. 3, the spill ring 32 moves leftward and the fuel injection amount decreases.

The pump housing 14 has an adjusting lever 39 for applying an operating force to the tension lever 37.
An (accelerator lever) is rotatably attached via a shaft 40. An eccentric pin 41 is attached to one end of a shaft 40 protruding into the pump chamber 20, and a control spring 42 for pulling the tension lever 37 in the leftward rotation direction in the drawing is provided between the eccentric pin 41 and the tension lever 37. Is intervening. The tension of the control spring 42 increases when the adjusting lever 39 is rotated toward the fuel amount increasing side, and decreases when the adjusting lever 39 is rotated toward the fuel amount decreasing side.

The control lever 34 is acted upon by the governor 4 utilizing centrifugal force. The governor 4 includes a governor shaft 43 fixed to the pump housing 14 so as to project into the pump chamber 20, and the governor shaft 43.
A governor sleeve 44 slidably fitted around the outer periphery of the
The flyweight 45 opened by centrifugal force is a main component.

The governor sleeve 44 has one end contacting the control lever 34 and the other end contacting the flyweight 45 via the washer 46. The governor sleeve 44 advances in the axial direction in conjunction with the opening operation of the flyweight 45 ( 3) and moves backward in the axial direction (moves to the left in FIG. 3) in conjunction with the closing operation of the flyweight 45. Fly weight 45
Is driven by a driven gear 47 that is driven by a drive gear 5 that rotates integrally with the drive shaft 2, and is opened and closed by the centrifugal force of the rotation.

The turning positions of the control lever 34 and the tension lever 37 are the same as those of the control spring 42.
And the pressing force of the flyweight 45 against the governor sleeve 44, and as a result, the position of the spill ring 32 is determined and the fuel injection amount is adjusted. That is, when the tension of the control spring 42 is kept constant, when the rotational speed of the drive shaft 2 increases, the fly weight 45 opens by the centrifugal force to move the governor sleeve 44 forward, and the control lever 34 moves to the control spring 42. Figure 3 against
To the right. As a result, spill ring 3
2 moves to the left in the drawing, and the fuel injection amount decreases. Conversely, when the rotation speed of the drive shaft 2 decreases, the centrifugal force acting on the flyweight 45 weakens, and the control spring 42 rotates the control lever 34 in the left rotation direction in FIG. As a result, the spill ring 32 moves to the right in the figure, and the fuel injection amount increases.

On the other hand, when the rotational speed of the drive shaft 2 is constant, the adjusting lever 39
When is rotated toward the fuel increase side, the tension of the control spring 42 increases, so that the control lever 34 rotates in the counterclockwise rotation direction in FIG. 3 and the spill ring 32 moves to the right in the figure, and the fuel injection amount is increased. To increase. At this time, the governor sleeve 44 retreats as the control lever 34 rotates, and the flyweight 45 closes accordingly. On the contrary, when the adjusting lever 39 is rotated toward the fuel amount reducing side, the tension of the control spring 42 is reduced, so that the pressing force of the governor sleeve 44 against the control lever 34 becomes relatively large. As a result, the control lever 34 rotates in the right rotation direction in FIG. 3, the spill ring 32 rotates in the left direction in the drawing, and the fuel injection amount decreases.

A timer device 25 for mechanically adjusting the fuel injection timing to advance or retard the fuel injection timing is provided below the pump housing 14. The timer device 25 changes the rotation position of the roller ring 8 with respect to the rotation direction of the drive shaft 2 to change the timing at which the cam crest 7a rides on and off the cam roller 9, that is, the timing at which the plunger 10 reciprocates. It is what makes me. In this way, the roller ring 8
So that the turning position can be changed by the timer device 25,
It is rotatably supported with respect to the pump housing 14.

The timer device 25 is driven by hydraulic pressure, and as disclosed in FIG. 1, the timer housing 50 which constitutes the lower part of the pump housing 14.
And a timer piston 51 fitted therein so as to be movable in the axial direction. This timer piston 51 is
It is connected to the roller ring 8 via a slide pin 52.

The slide pin 52, as shown in FIG.
It has a cylindrical rod shape, one of which is inserted through the roller ring 8 and the other of which is inserted into the timer piston 51, which transmits the axial movement of the timer piston 51 to the roller ring 8 to rotate the roller ring 8. Change the position. Since the coupling 6 is provided on the upper end side of the slide pin 52, the slide pin 52 is roller-rolled by a clip 54 having a retaining pin 53 in order to prevent the upper end of the slide pin 52 from coming into contact with the coupling 6. It is attached to 8. Reference numeral 52a shown in FIG. 2 is a hole through which the retaining pin 53 is inserted.

The torque of the timer piston 51 is applied between the slide pin 52 and the timer piston 51.
2, and a sub-piston 55 for preventing abrasion of the slide pin 52 and the timer piston 51 is inserted. The abrasion resistance treatment of the slide pin 52 at the portion fitted with the roller ring 8 will be described later.

One end of the timer piston 51 is a timer low pressure chamber 26 communicating with the introduction port 24, and the other end of the timer piston 51 is a timer high pressure chamber 57 communicating with the pump chamber 20 via an orifice 56. There is. In the timer low pressure chamber 26, the timer piston 51 is attached to the timer high pressure chamber 5
A timer spring 58 for urging the No. 7 side is arranged. On the other hand, the fuel pressurized in the feed pump 3, that is, the fuel in the pump chamber 20 is introduced into the timer high pressure chamber 57. Then, the position of the timer piston 51 is determined by the balance between the introduced fuel pressure and the urging force of the timer spring 58. By thus determining the position of the timer piston 51, the roller ring 8
Is determined, and the advance timing for reciprocating the plunger 10 is determined.

The timer device 25 includes a timer piston 51.
Control valve (hereinafter, T
CV) 59 is provided. The TCV 59 controls the pressure difference between the timer high pressure chamber 57 and the timer low pressure chamber 26, and controls the opening and closing of the communication passage that connects the timer high pressure chamber 57 and the timer low pressure chamber 26. TCV59
Is opened and closed by a duty-controlled electric signal to control the pressure difference between the timer high-pressure chamber 57 and the timer low-pressure chamber 26 to drive the timer piston 51, so that the reciprocating timing of the plunger 10 is advanced or retarded. To control to.

Next, the abrasion resistance treatment of the slide pin 52 at the portion fitted to the roller ring 8 will be described.
As described above, the slide pin 52 transmits the torque of the timer piston 51 hydraulically driven to the roller ring 8. Here, if the fuel injection pressure is increased, the rotational load of the roller ring 8 increases. For this reason, the slide pin 52 that rotates the roller ring 8 is attached to the roller ring 8.
Excessive load acts on the fitting part of and. When the slide pin 52 vibrates slightly in such a state, the slide pin 52 is fretting worn at the fitting portion with the roller ring 8 under the condition that the lubricity of the fuel is lowered.

Therefore, the slide pin 52 is subjected to a hardening treatment for increasing the abrasion resistance on the surface of the slide pin 52 in order to prevent abrasion. Specifically, the slide pin 52 is formed of aluminum-chromium-molybdenum steel instead of conventional chromium-molybdenum steel, and first, the strength of the internal structure is enhanced by quenching and tempering treatment, and then the nitriding treatment is performed to increase the surface strength. I am raising.

An example of the quenching treatment and the tempering treatment will be shown. Quenching treatment is 870 ° C. for 40 minutes. The tempering treatment is 500 ° C. for 90 minutes. An example of nitriding treatment will be shown. Nitriding treatment is performed in a nitrogen atmosphere at 520 ° C. for 35 hours.

After the nitriding treatment, the outer peripheral surface of the slide pin 52 is cut to remove the porous layer produced during the nitriding treatment.

[Effects of Embodiment] As described above, the slide pin 52 is formed of aluminum / chromium / molybdenum steel and subjected to the nitriding treatment.
Surface strength of 1.5 times that of conventional products (Hv = 950-1
200) can be hardened. Therefore, it is possible to suppress fretting wear of the slide pin 52 even under the condition that the lubricity is lowered due to the high injection pressure of fuel and the low sulfur of fuel. As described above, by suppressing the wear of the slide pin 52, the occurrence of an operation error of the timer device 25 can be suppressed, the roller ring 8 can be accurately rotated by the timer device 25, and the injection timing can be maintained for a long time. Therefore, it is possible to accurately control to the advance side or the retard side.

That is, even if the fuel injection pressure is increased or low lubricity fuel is used, the advance control by the timer device 25 can be accurately performed for a long period of time. Therefore, it is possible to prevent the occurrence of engine output shortage due to insufficient advance angle and the deterioration of exhaust gas. Further, since the generation of abrasion powder from the slide pin 52 is suppressed,
It is possible to avoid the problem that the abrasion powder is caught in the sliding portion of the plunger 10 or the like and causes poor sliding or sticking.

Further, the slide pin 52 of this embodiment is
Is a slide pin 52 that has been quenched and tempered.
Since the internal structure of is improved and the strength is increased, even if an excessive load acts on the slide pin 52 for a long period of time, there is no problem of fatigue damage to the slide pin 52.

[Second Embodiment] In the first embodiment described above, an example in which the surface strength of the slide pin 52 is increased by nitriding treatment is shown. However, in the second embodiment, the slide pin 52 is made of chromium as in the conventional case. It is made of molybdenum steel, and its surface is coated with chromium nitride (CrN). Thus, even if the surface of the slide pin 52 is coated with chromium nitride (CrN), it is effective in suppressing the wear of the slide pin 52 as in the first embodiment. Also,
The method of coating the surface of the slide pin 52 with chromium nitride (CrN) as in the second embodiment can be applied to the conventional slide pin 52, and the cost can be suppressed.

[Modification] In the above embodiment, nitriding treatment and chromium nitride (CrN) coating are shown as an example of the treatment for increasing the surface strength of the slide pin 52, but tungsten carbide carbon ( WC /
The surface strength of the slide pin 52 may be enhanced by another treatment such as coating C) or performing a plating treatment such as NiP plating to enhance the surface strength. In the above embodiment, an example in which the centrifugal governor 4 is used to mechanically adjust the fuel injection amount has been described. However, instead of the governor 4, a distributed fuel injection pump that adjusts the fuel injection amount by a spill solenoid valve is used. The present invention may be applied to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a coupling and a timer device.

FIG. 2 is a perspective view of a slide pin.

FIG. 3 is a sectional view of a distribution type fuel injection pump.

[Explanation of symbols]

1 Distribution type fuel injection pump 8 roller ring 14 Pump housing 20 pump room 25 timer device 51 timer piston 52 Slide pin

Claims (4)

[Claims] 1. A roller ring rotatably supported by a pump housing forming a pump chamber, and a slide pin having one end inserted through the roller ring and the other end protruding outside the roller ring. The other end side of the slide pin is inserted, and a timer piston for driving the slide pin is provided, and by driving the timer piston in the axial direction, the roller ring is rotated to inject fuel. The distribution type fuel injection pump according to claim 1, wherein the surface of the slide pin is subjected to a hardening treatment for increasing abrasion resistance. 2. The distributed fuel injection pump according to claim 1, wherein the slide pin is made of aluminum / chromium / molybdenum steel, and the hardening treatment is a nitriding treatment at a high temperature. A distributed fuel injection pump characterized in that 3. The distributed fuel injection pump according to claim 1, wherein the slide pin is made of chromium molybdenum steel, and the hardening treatment is a coating of chromium nitride. Injection pump. 4. The distributed fuel injection pump according to claim 2 or 3, wherein the slide pin has been subjected to a quenching process and a tempering process.