JPH05141320A - Pre-stroke variable distribution type fuel injection pump - Google Patents

Abstract

PURPOSE:To provide pre-stroke variable control with extremely simple structure by overlapping pre-stroke control slits formed in the plunger rotating direction with suction slits of a barrel at the cam lift start only when an advance timing is zero. CONSTITUTION:There is provided a plunger 7 which is rotated according to rotation of an engine and makes reciprocating motion by means of a disk cam 8 whose timing is advanced by means of a timer 19. The plunger 7 is also provided with suction slits 71 equivalent to the number of cylinders. Pre-stroke control slits 1 having length of not reaching adjacent suction slits 71 are formed in the plunger rotating direction in a suction slit area of the plunger 7 so as to continue perpendicularly to respective suction slits 71. These pre-stroke control slits 1 are set to overlap with a suction slit 61 of a barrel 6 at the cam lift start only when an advance timing is zero. Thereby, pre stroke variable control can be realized with extremely simple structure.

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, and more particularly to a prestroke variable distribution type fuel injection pump with mechanical position control.

[0002]

2. Description of the Related Art In a distributed fuel injection pump of a diesel engine, it is effective to increase the fuel injection pressure at low speed and high load as a measure against steady smoke and free accelerator smoke. As a method of this, there is a method of using a cam with a high oil feeding rate.In this case, although the fuel injection pressure at low speed and high load can be increased, the fuel injection pressure at high speed and high load is more than necessary Therefore, there is a problem that the durability of the cam becomes less than the allowable value, or the load of the drive unit exceeds the allowable torque due to a large increase in the driving torque. As a countermeasure for this, while using the high oil transfer rate cam, the cam use position is changed, and at low speed and high load, the part A where the cam speed is fast in the cam speed diagram of FIG. The slower speed part B is used, the pre-stroke is increased in the former and the pre-stroke is decreased in the latter, thereby controlling the fuel injection amount per unit cam angle (fuel injection rate) while avoiding an excessive increase in injection pressure. A variable pre-stroke method has been proposed. A typical example thereof is JP-A-63-285.
No. 244 (Prior Art 1) and JP-A No. 62-29731 (Prior Art 2).

[0003]

In the prior art 1, the fuel pressurizing chamber above the plunger is connected to the pump chamber through the relief passage and the passage-like low pressure chamber provided in the barrel and the distributor head, and the low pressure is established. A pre-stroke is made variable by providing a solenoid valve in the chamber and opening and closing between the high pressure chamber and the low pressure chamber by this solenoid valve. However, since the prior art 1 uses an expensive actuator called a solenoid valve, the cost is greatly increased. Moreover, the response speed and opening / closing frequency of ultra-high speed (for example, 4 cylinders, 2500 rpm is 1
Since it needs to be opened and closed 10,000 times a minute), there is a problem that the reliability is poor such that the operation becomes unstable and the variation increases due to long-term use. In the prior art 2, first and second cutoff ports are formed in the plunger portion below the barrel, and these ports are opened and closed by the first and second control sleeves fitted on the plunger. The displacement amount of the first control sleeve for controlling the start is controlled by the pre-stroke control lever. However, this prior art 2
Has a problem that the length of the plunger is increased due to the use of two control sleeves, a dead volume including a vertical hole of the plunger is increased, and a size of the pump is increased.

[0004]

SUMMARY OF THE INVENTION The present invention was devised to solve the above-mentioned problems, and the purpose of the present invention is to add a new actuator without adding a large pump or plunger. With a very simple structure, variable pre-stroke control can be realized, and flat injection pressure characteristics below the limit pressure with respect to pump rotation can be obtained, improving low-speed and high-load emissions. Another object of the present invention is to provide a pre-stroke variable distribution type fuel injection pump capable of satisfying both reliability of pressure resistance and pressure resistance.

In order to achieve the above object, the present invention devises the slit structure of the plunger and makes the prestroke variable by utilizing this slit and the change of the suction port opening due to the advance of the timer. That is, the present invention has a plunger that rotates according to the rotation of the engine and that reciprocates by a disc cam that is advanced by a timer,
The plunger has suction slits for the number of cylinders, and sucks fuel when this plunger matches the suction slit of the barrel,
In a fuel injection pump of a type that pressurizes and feeds together with a lift of a plunger, a plunger is provided with a pre-stroke control slit in a suction slit region of the plunger, the pre-stroke control slit having a length that extends vertically to each suction slit and does not reach an adjacent suction slit. The pre-stroke control slits are formed in the rotational direction so that the pre-stroke control slits overlap the suction slits of the barrel at the beginning of the cam lift only when the advance angle is zero.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 show an example of a distributed fuel injection pump according to the present invention. In FIG. 2, 2 is a pump housing, 3 is a drive shaft, 4 is a feed pump, and fuel oil is supplied into the pump chamber 5 by the feed pump 4. 6 is a plunger barrel (hereinafter simply referred to as a barrel) fitted and fixed to the pump housing 2 coaxially with the drive shaft 3,
A plunger 7 is slidably inserted in the barrel 6, and a pressurizing chamber 14 is defined between the tip of the plunger 7 and the barrel.

The plunger 7 is integrally rotated by being coupled to a cam disk 8 by a coupling, and the cam disk 8 has cam surfaces as many as the number of cylinders of the engine. Since the surface rolls on the roller 11 mounted on the roller holder 10 in the pump housing, the movement of the cam disk 8 causes the plunger 7 to move.
Is reciprocated per one revolution according to the number of cylinders of the engine. A high oil transfer rate cam is suitable as the cam.

A number of suction slits 71 corresponding to the number of cylinders are formed in the axial direction on the outer peripheral surface of the tip of the plunger 7, and the suction slits 61 formed in the plunger barrel 6 communicate with each other during the suction stroke, so that the pump is pumped. The fuel in the chamber 5 is sucked into the pressurizing chamber 14 from the supply passage 13. Further, a vertical hole 70 is formed in the plunger 7 in the axial direction from the center of the front end surface, and a single outlet slit 73 branched from the vertical hole 70 is formed at an intermediate portion in the axial direction of the plunger, so that the plunger 7 is lifted. When the suction slit 61 is closed by rotating the pressurizing chamber 1,
The fuel oil of No. 4 is pressurized and starts to be pumped when it coincides with the outlet port 15 of the barrel 6, is pumped from the discharge passage 22 through the delivery valve 16 to the injector, and is injected.

Reference numeral 18 denotes a control sleeve, which is externally fitted to a plunger portion protruding from the barrel 6 and is slidable with respect to the plunger by a governor mechanism 17. When the plunger 7 is lifted by the cam disk 8 and the cut-off port 74 branched from the vertical hole 70 is seen from the edge, the control sleeve 18 returns the fuel in the plunger to the pump chamber 5 and terminates the pressure feeding. The displacement of the control sleeve 18 changes the effective stroke of the plunger 7. In this embodiment, the governor mechanism 17 is a mechanical type, but of course an electric governor may be used.

A timer 19 has a hydraulically actuated timer piston 20, and the timer piston 20 has a pin 21.
Is connected to the roller holder 10 via a pump chamber 5
The timer piston 20 is displaced according to the change in pressure, and the peak of the cam surface of the cam disk 8 is brought closer to the roller earlier, so that the injection timing is advanced (advanced) or, conversely, delayed (delayed). The timer 19 may use an electronically controlled type combined with a timing control valve.

The above structure is similar to that of the conventional distributed fuel injection pump. The present invention is characterized in that the pre-stroke control slit 1 that is not ring-shaped but protrudes radially for each suction slit 71 is formed on the outer peripheral surface of the plunger 7, especially in the region where the suction slit 71 is formed. is there. 1, 3, 4, and 5 show the details. The pre-stroke control slit 1 is provided at a position facing the suction slit 61 of the barrel 6 in the plunger bottom dead center state in the axial direction. The pre-stroke control slit 1 is provided in a vertical relationship with respect to the suction slit 71, and is provided on the leading side with respect to the rotation direction of the plunger 7 as shown in FIG. But,
As shown in FIG. 5B, the prestroke control slit 1 has a length l that does not reach the adjacent suction slit 71.
And each suction slit 71 is independent. The length l of the prestroke control slit is a region where the suction slit 61 of the barrel 6 can be located between the tip of the prestroke control slit and the suction slit 71 adjacent thereto.
(Closed hole area) E is set so that it can be formed.

[0012]

Next, the operation of the present invention will be described. During the intake stroke of the plunger 7, the fuel oil in the pump chamber 5 is supplied to the supply passage 1
3 through the suction port 60 and the suction slit 61, and is sucked into one of the suction slits 71 of the plunger 7 and fed into the pressurizing chamber 14, and the suction slit 71 is cut off from the suction slit 61 in the pressure-feeding stroke, The fuel oil inside is pressurized and discharged from the outlet slit 73 to one of the outlet ports 22. This basic operation is the same as that of a general-purpose distributed fuel injection pump.

The feature of the present invention is that the pre-stroke is realized by the slit structure formed in the plunger, and
This is done by utilizing the change in the opening of the suction port due to the slit and the advance angle. That is, in the present invention, as the cam use position, in FIG. 6, the area A is the use cam position at high speed and high load, and the area B is the use cam position at low speed and high load. A timer sets the advance angle to zero at low speeds and high loads and fully advances it at high speeds and high loads, which causes a slower lift phase of the plunger, which causes the intake slit 61 of the barrel and the prestroke control slit 1 Overlap or no overlap. Since the overlap period is a non-pressure feeding stroke, it is possible to inject fuel at high pressure in a short period. In FIG. 5, (a) shows the relationship between the cam lift phase at zero advance and full advance and the suction port opening state, where is the cam lift phase line at zero advance and is the cam lift phase at full advance. The line indicates the suction port opening line at the time when the lead angle is zero and the full advance angle, and the line indicates the suction port opening line when the lead angle is zero. (B) shows the overlapping relationship between the plunger suction slit 71 / pre-stroke control slit 1 and the barrel suction slit 61 when the advance angle is zero in the plunger unfolded state, and the symbols (a) to (g) are (a).
It corresponds to the opening diagram positions of a to g shown in FIG. (C) shows the overlap relationship between the plunger suction slit 71 / pre-stroke control slit 1 and the barrel suction slit 61 at the time of full advance in the plunger unfolded state, and the symbols (a ′) to (g ′) are (a). ) Corresponds to the opening diagram positions of a'to g '. In (b) and (c), the plunger rotates to the left. Needless to say, the position of the suction slit 61 of the barrel is fixed.

First, when the timer advance angle is zero, the plunger suction slit 71 becomes the barrel suction slit 61 as shown in FIG.
The pre-stroke control slit 1 is directly above the barrel suction slit 61. Then, when the plunger approaches the top dead center, the plunger suction slit 71 starts to wrap with the barrel suction slit 61 by the rotation of the plunger, and the wrap amount gradually increases. Then, when the plunger or the top dead center is passed, the plunger suction slit 71 and the barrel suction slit 61 are 100% as shown in (b).
% Overlap. As a result, the fuel from the pump chamber is sucked into the pressurizing chamber 14.

While the plunger 7 returns to the bottom dead center state, the lap amount between the plunger suction slit 71 and the barrel suction slit 61 decreases as shown in (c), the wrap amount becomes zero at the bottom dead center, and the suction stroke ends. .. The plunger 7 rotates during the start of the next lift cycle. At this time, the barrel suction slit 61 is closed by the outer peripheral surface of the plunger, and the prestroke control slit 1 faces the side of the barrel suction slit 61. .. Then, as the plunger rotates, the tip of the pre-stroke control slit 1 gradually approaches the side edge of the barrel suction slit 61 as shown in (d) and (e). Then, the plunger then starts to lift while rotating, but the phase at which the lift is started is later than the advance phase. Therefore, the prestroke control slit 1 overlaps with the barrel suction slit 61 from the start of the lift, and the overlap amount continuously changes with the lift of the plunger. (f) shows a point on the way, and the prestroke H is created by the communication between the prestroke control slit 1 and the barrel suction slit 61, and the pressure in the pressurizing chamber 14 is lowered, so that the fuel oil is pumped. Not done. Thereafter, the plunger 7 is further lifted, so that the barrel suction slit 61 is closed by the outer peripheral surface of the plunger under the prestroke control slit 1 as shown in (g), and fuel pressure feed is started. Therefore, fuel injection is performed for a short period under high injection pressure conditions.

On the other hand, when the timer is fully advanced, the port overlap relationship between the end of the suction stroke and the plunger bottom dead center is almost the same as when the advanced angle is zero. However, at this full advance angle, as is apparent from FIG. 5A, the cam lift phase is earlier than at zero advance angle. That is, the lift start time of the plunger becomes relatively early.
Therefore, even though the pre-stroke control slit 1 is located at the plunger rotational movement position that originally overlaps the barrel suction slit 61, the accuracy plunger lift amount per unit crank angle is large, so that the pre-stroke control as shown in (f ') is performed. The slit 1 and the barrel suction slit 61 do not overlap. Therefore, in this case, the prestroke is not created, and the fuel oil is pressurized and sent under pressure from the start of the lift of the plunger. It should be noted that the prestroke increases from zero advance angle to full advance angle as the advance angle approaches zero.

[0017]

According to the present invention described above, a prestroke control slit having a length perpendicular to the suction slit region of the plunger and not reaching the adjacent suction slit is provided in the plunger rotation direction so as to control the prestroke. The structure is designed so that it overlaps with the suction slit of the barrel at the beginning of the cam lift only when the slit has a zero advance angle, so there is no need to add a new actuator, and the pump and plunger do not become large, and the structure is extremely simple. It is possible to realize variable prestroke with
Since the position control is performed, the operation is stable and the variation can be reduced. Further, since the present invention can obtain a flat injection pressure characteristic with respect to the pump rotation, it becomes possible to improve both low-speed and high-load emissions and to secure pressure resistance, especially when it is applied to direct injection specifications. Since the prestroke is large on the low speed side and the prestroke is small on the high speed side, excellent effects such as matching with the direction in timing control can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a pump end portion according to the present invention.

FIG. 2 is a sectional view showing an example of a distribution type fuel injection pump using the present invention.

FIG. 3 is a sectional view of a plunger and a barrel according to the present invention.

FIG. 4 is a partially cutaway plan view of the plunger according to the present invention.

FIG. 5A is a diagram showing a relationship between a cam lift phase and an intake port opening when the present invention is applied, and FIG. 5B is a development view showing stepwise slit overlap at a lead angle of zero. (C)
[FIG. 8] is a development view showing stepwise the slit overlap at the time of full advance.

FIG. 6 is a cam velocity diagram showing a cam use position.

[Explanation of symbols]

 1 pre-stroke control slit, 6 barrel, 7 plunger, 8 disc cam, 19 timer, 61 suction slit, 71 suction slit

Claims (1)

[Claims] 1. A plunger which rotates in response to rotation of an engine and reciprocates by a disc cam advanced by a timer, the plunger having suction slits corresponding to the number of cylinders, which are suction slits of a barrel. In a fuel injection pump of the type that sucks fuel when it matches, pressurizes it with a lift of a plunger, and pumps it, it communicates with the suction slit area of the plunger perpendicularly to each suction slit, and does not reach an adjacent suction slit. A pre-stroke control slit having a length is formed in the plunger rotation direction, and the pre-stroke control slit is configured to overlap with the suction slit of the barrel at the beginning of the cam lift only when the advance angle is zero. Variable stroke type fuel injection pump.