JPS6045748B2 - distribution type fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distribution type fuel injection pump for an internal combustion engine, and particularly to one that has improved fuel injection characteristics depending on engine operating conditions.

BACKGROUND ART In fuel injection internal combustion engines such as diesel engines, it is necessary to control the amount and timing of fuel injection depending on the engine operating state.

In other words, when starting the engine, the injection amount is increased to improve starting performance, when idling the injection amount is decreased, and when the engine is running at high speed, the injection amount is increased as the load increases.
Injection starts earlier as the rotation speed increases.

In a distribution type fuel injection pump, the injection amount related to the rotational speed is controlled by a control sleeve that is slidably attached to the plunger that performs the pump action and is moved by a centrifugal governor that responds to the engine rotational speed. This is done by changing the position of the plunger where the cut-off port of the fuel pumping passage is disengaged from the control sleeve and communicates with the low pressure source to end the injection.

However, in such injection amount control, there is a limit to the amount of lift of the flyweight that corresponds to the amount of movement of the control sleeve, so it is difficult to sufficiently increase the amount of lift from starting to idling. Insufficient amounts of water sometimes adversely affected starting performance.

Also, when starting, advancing the fuel injection angle compared to when idling J will lead to improved startability, but with the conventional rotation speed timer (which advances the injection angle as the engine speed increases), It cannot be controlled.

Furthermore, when idling, the combustion air temperature is low and the ignition delay is large, so the conventional configuration that controls the injection amount while keeping the injection rate constant will result in idle knock, which is extremely disadvantageous in terms of noise control. It was hot. For this reason, as shown in Japanese Patent Application Laid-open No. 51-98426, a part of the fuel pressurized by the plunger during idling is relieved to the low pressure side through a throttle part to reduce the injection rate. Some devices are designed to prevent knocking.

However, since the fuel discharge passage is opened and closed by a solenoid valve, the structure is complicated and costly, and the solenoid valve with the structure shown in this publication has difficulty withstanding the extremely high fuel pressure caused by the plunger. (Fuel leaks occur even when the solenoid valve is closed.) In order to withstand this, the structure of the solenoid valve becomes even more complicated, resulting in higher costs.

Furthermore, since the engine operates in the same way as when idling and the exhaust passage is opened during startup, it is impossible to increase the fuel injection amount by receiving a pre-stroke from the plunger, making it impossible to improve startability.

The present invention has been made to solve these conventional problems, and it improves starting performance by increasing the amount of fuel injected at the time of starting and advancing the injection advance angle, and also reduces the fuel injection pressure at idling to perform injection. Combustion noise is suppressed by lowering the combustion rate, and by controlling this using a control valve that responds to fuel supply pressure related to engine speed, distribution is simple, low-cost, and highly reliable. The present invention provides a type fuel injection pump. The present invention will be explained below based on an embodiment shown in the drawings.

In FIG. 1, fuel is sucked and pressurized from a fuel tank 1 by a feed pump 2, and is supplied to a suction space 4 within a pump housing 3.

feed. Since the pump 2 is driven by the engine, the fuel oil pressure within the suction space 4 increases as the engine speed increases. The maximum value of the oil pressure is controlled by a pressure control valve 5. A pump/distribution plunger 7 is slidably inserted into a plunger barrel 6 provided through the pump housing 3, and this plunger 7 is caused to reciprocate and rotate as described below.

That is, a cam disk 8 integrated with the plunger 7 is rotated by a drive shaft driven by the engine via a driving disk (all not shown). The cam disk 8 has a cam surface in which a number of peaks corresponding to the number of cylinders of the engine are equally spaced, and this cam surface is attached to a plunger spring (
(not shown), the cam disk 8 and therefore the plunger 7 perform a constant reciprocating motion at the same time as rotation. When the plunger 7 is in the suction stroke where it moves downward as shown in the figure, the head of the plunger 7 and the closing plug 1
The volume of the pump chamber 11 formed between the pump chamber 11 and the pump chamber 11 increases.

At this time, one of the plurality of vertical grooves 12 provided on the outer peripheral surface of the head of the plunger 7 faces the other end of the suction passage 13 whose one end is opened to the suction space 4, so that the pump chamber 11
fuel is inhaled. When the plunger 7 shifts to the pressure stroke where it moves upward in the figure, the suction passage 13 is separated from the vertical groove 12, and the fuel sucked into the pump chamber 11 is transferred from the passage 14 that runs vertically through the center of the plunger 7. It is delivered to a passage 16 penetrating the plunger barrel 6 and pump housing 3 through a distribution vertical groove 15 formed on the outer circumferential surface of the plunger 7, and is then forced through a delivery valve 17 to an injection nozzle 18 and injected into the cylinder. Ru. Incidentally, since the number of passages 16 corresponding to the number of cylinders is equally distributed in the circumferential direction, fuel is injected into each cylinder in a predetermined order as the plunger 7 reciprocates and rotates. Further, a cut-off boat 19 is provided in a portion of the plunger 7 that projects toward the suction space 4 side, and a cut-off boat 19 is provided to communicate the passage 14 with the suction space 4, and a control sleeve 20 is slidably attached to this portion. The cut-off boat 19 is closed on the inner peripheral surface of the cut-off boat 19.

Therefore, the plunger 7 moves upward and the cutoff boat 19
When the control sleeve 20 comes off the upper edge and opens into the suction space 4, the fuel in the passage 14 flows out from the cut-off boat 19 into the suction space 4, so that the passage 16
Delivery to is stopped and injection ends. The control sleeve 20 is engaged with a lever 21 that is swung by an operation input mechanism that sets the rotational speed of the engine and a centrifugal speed governor mechanism that detects the rotational speed of the engine (both omitted). When setting the engine speed to a low speed, or when the engine is rotating at a higher speed than the set speed, the control sleeve 20 is moved downward as shown in the figure to speed up the end of injection and thereby reduce the injection amount. Here, an annular groove that intersects and communicates with the suction passage 13 is provided on the outer peripheral surface of the plunger barrel 6, and a chamber 22 is formed between the plunger barrel 6 and the barrel insertion hole of the pump housing 3.
A sliding hole 23 is formed in the pump housing 3 from the outside.
is bored, and the tip of the sliding hole 23 is communicated with the chamber 22 via a small-diameter communication hole 24.

A piston 25 is slidably inserted into this sliding hole 23,
A chamber 26 is formed by the head of the piston 25 and the sliding hole 23. A compression spring 27 is interposed at the end of the piston 25, and a closing plug 28 is attached to the outer end of the sliding hole 23. The plug 28 is formed with an internal passage 30 whose one end opens into the chamber 29 on the end side of the piston 25, and the other end of the internal passage 30 is connected to the low pressure side of the feed pump 2 via a spill tube 31. It is connected to.
A communication passage 32 passes through the plunger barrel 6 and the pump housing 3 and has one end opening into the pump chamber 11 and the other end opening into the inner peripheral surface of the sliding hole 23, and a barrel whose one end slides into contact with the plunger 7. 6, and a communication path 33 whose other end is open to the inner circumferential surface of the sliding hole 23 is formed.

Further, an annular groove 34 is formed on the outer circumferential surface of the plunger 7 to match one opening end of the communication passage 33 near the bottom dead center of the plunger 7, that is, at a position where the distribution vertical groove 15 begins to match the opening end of the passage 16; The annular groove 34 is communicated with the passage 14 via a horizontal hole 35. Here, the communication path 32, the sliding hole 23, the chamber 29,
The internal passage 30 and the spill tube 31 constitute a first relief passage that communicates the pump chamber 11 with a low pressure source, and the horizontal hole 35, the annular groove 34, the communication passage 33, the sliding hole 23, and the chamber 26.
, the communication hole 2 chamber 22 connects the fuel pressure feeding passage 14 to the suction space 4 which is a low pressure source via the suction passage 13 at the beginning of the fuel feeding stroke.
A second relief passage is configured to communicate with the second relief passage. piston 25
Two annular grooves 36 and 37 are formed on the outer peripheral surface of the piston 25, and these annular grooves 36 and 37 are formed at a predetermined stroke position of the piston 25.
, 37 are opposed to the open ends of the communicating passages 32, 33, respectively,
At a position where the piston 25 is closer to the plug 28 than this, the annular groove 37 on the end side of the piston 25 formed wide still faces the open end of the communication passage 33, but the annular groove 37 on the head side of the piston 25 is connected to the communication passage 32. It is designed so that it can come off from the open end of. (See FIG. 2) One annular groove 36 includes a constriction part 38a inside the piston 25 and communicates with the chamber 29 via a passage 38 bored in a crisscross manner.
communicates with the chamber 26 via an L-shaped passage 39 formed in the piston 25.

According to this configuration, at the time of starting the aircraft, the hydraulic pressure introduced from the suction space 4 through the chamber 22 to the chamber 26 on the head side of the piston 25 is low, and the piston 25 is urged by the spring 27 to move to the left from the illustrated position. and piston 25 of 2
Both annular grooves 36 and 37 are blocked. That is, at the time of starting, the piston 25 (control valve) shuts off the first and second relief passages. Therefore, from around the bottom dead center of the plunger 7 until the cut-off boat 19 comes off the upper edge of the control sleeve 20, the fuel flows from the distribution groove 15 to the injection nozzle 18 through the passage 16 and the delivery valve 17 under normal pressure. It is sent out and injected into the combustion chamber of the engine.

Next, mainly in the low rotation range such as when idling, the hydraulic pressure increases to a certain extent, so the pressure in the chamber 26 increases accordingly, causing the piston 25 to move to the right relative to the time of startup and reach the position shown in the figure. The open ends of the passages 32, 33 fit into the annular grooves 36, 37 of the piston 25, respectively.

As a result, the first relief passage is connected to the annular groove 36 and the passage 38.
The second relief passage opens through the internal passage of the piston (control valve) 25 consisting of the annular groove 37 and the passage 3.
It opens through the internal passage of the piston (control valve) 25 consisting of 9. Therefore, at the beginning of the fuel discharge stroke, the plunger 7
When is located near the bottom dead center, the annular groove 3
4 coincides with the open end of the communication passage 33, the fuel is discharged through the second relief passage into the suction space 4 on the low pressure side, and is not supplied to the injection nozzle 18, which has a large flow resistance.

Then, at the same time that the annular groove 34 disengages from the open end of the communication passage 33, fuel injection is started with a delay of a stroke Sp (hereinafter referred to as pre-stroke) in which the annular groove 34 and the communication passage 33 overlap with respect to the time of starting. Ru. At the same time, a portion of the fuel in the pump chamber 11 flows out through the first relief passage while being throttled to a low pressure source such as the low pressure side of the feed pump, so that the increase in fuel pressure in the pump chamber 11 is suppressed to a certain level. The outflowing fuel is corrected by the speed governor and the injection time is extended, so the injection rate is lowered, thus making it possible to lower the combustion speed and reduce combustion noise.
When the engine speed further increases and the piston 25 moves to the right from the illustrated position due to the accompanying pressure increase in the chamber 26, the annular groove 37 remains open to the communication passage 33 as described above, but the annular groove 36 It gets cut off again.

That is, in such a medium/high speed rotation range, the outflow of fuel from the pump chamber 11 through the communication passage 32 is stopped, so that the pump chamber 1
1 internal pressure is kept at normal pressure, and injection starts with plunger 7.
The stroke position is delayed by the ratio prestroke at the time of starting, similar to when idling, but the piston position in the combustion chamber is advanced by a timer (not shown) as the speed increases.

In such a configuration, if the injection advance angle is set based on the injection advance angle at idling, at the time of starting, the fuel injection amount will be increased by the amount of prestroke compared to the conventional one, and the amount of fuel injection will be increased by the amount of prestroke compared to idling. Since the advance angle is advanced, starting performance is improved, and when idling, the fuel injection rate is lowered as described above to lengthen the injection time and reduce combustion noise, and at high speeds, the normal advance due to the normal pressure and timer is reduced. It can be sprayed with angular characteristics.

As explained above, the present invention improves the fuel injection characteristics according to the engine speed, and in particular increases the fuel injection amount and advances the injection angle, thereby improving starting performance and reducing the fuel injection rate. This makes it possible to reduce combustion noise during idling as much as possible.

In addition, these characteristics are improved using a control valve that operates using hydraulic pressure related to the engine speed generated in the suction space of the distribution type fuel injection pump, compared to a control valve that uses a solenoid valve or the like. It is easy to configure, can be implemented at low cost, and has excellent reliability.
There is an advantage that startability can be improved by applying a pre-stroke to the plunger using a single hydraulic piston to increase the fuel injection amount and advance the injection angle.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a hydraulic circuit of a distribution type fuel injection pump according to the present invention, and FIG. 2 is an enlarged view of the main part of the same figure. 4... Suction space, 7... Plunger, 11... Pump chamber, 14... Passage, 2
2...Annular groove, 24...Communication hole, 25
...Zeston, 26...Room, 30...
...Internal passage, 32, 33...Communication passage, 34
...Annular groove, 35...Horizontal hole, 36, 37
......Annular groove, 38, 39...Passway.

Claims (1)

[Claims] 1. A distribution type fuel injection pump that sucks in, pressures and distributes fuel using a reciprocating and rotating plunger, which includes a first relief passage with a large throttling effect that connects a pump chamber defined by the plunger to a low pressure source, and the pump A second relief passage is provided which communicates the fuel pressure passage formed in the plunger with the chamber and connects it to a low pressure source at the beginning of the fuel pressure stroke, while a second relief passage is provided between the first and second relief passages to prevent engine rotation. In response to the fuel supply pressure related to the number of
A control valve is provided with an internal passage so as to shut off the first and second relief passages at startup, open both relief passages at a predetermined low speed range, and open only the second relief passage at higher speeds. A distribution type fuel injection pump characterized by: