JPS636429Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection timing control device for a distributed fuel injection pump of a diesel engine.

Conventionally, in a distribution type fuel injection pump for a diesel engine, for example, as shown in FIG. 1, a feed pump 2 driven by a drive shaft 1 sucks in fuel, pressurizes it, and guides it to a pump chamber 4 in a pump housing 3. The fuel pressure in the pump chamber 4 is controlled by a regulating valve 5 in substantially direct proportion to the rotational speed of the pump. Further, the fuel is supplied to a plunger 6 that reciprocates while rotating.
It is sucked into the chamber 7 at the tip, after which it is compressed by the plunger 6 and is injected from a nozzle (not shown) via a delivery valve 8 according to the injection order.

A roller holder 1 contacts a cam disk 9 that moves integrally with the plunger 6 via a roller 10.
1 is rotated by a timer piston 14 (described later), and the injection timing is controlled by adjusting the lift position of the plunger 6 relative to the engine side crank angle.

That is, the timer piston 1 has a pin 12 fixed thereon by protruding radially from the roller holder 11, and the tip of the pin 12 is slidably disposed within a cylinder 13 formed integrally with the outer wall of the pump housing 3.
It is engaged with the middle part of 4. Then, the fuel in the pump chamber 4 is introduced into one chamber 15 in the cylinder 13 partitioned by the timer piston 14 through a fuel introduction hole 16 with an orifice 16a formed in the timer piston 14, and the fuel pressure is applied to the timer piston 14. It is working. The other chamber 17 houses a spring 18 and the timer piston 1.
4, and this chamber 17 is connected to the communication path 1.
9 communicates with the low pressure side (the suction side of the feed pump 2).

In FIG. 1, for convenience of explanation, the axis of the timer piston 14 is shown rotated by 90 degrees, and the axis of the feed pump 2 is also shown rotated by 90 degrees.

Thus, the fuel pressure in chamber 15 and the spring 18
The timer piston 14 is moved in balance with the force, and the roller holder 11 is rotated via the pin 12. For example, by moving the timer piston 14 to the left in the figure due to an increase in fuel pressure in the chamber 15, The injection timing is advanced. Here, the fuel pressure in the chamber 15 is almost the same as the fuel pressure in the pump chamber 4, and the fuel pressure in the pump chamber 4 changes almost in direct proportion to the pump rotation speed, so the relationship between the pump rotation speed and the fuel pressure in FIG. The lead angle characteristics as shown are obtained.

However, with such conventional injection timing control devices, the advance angle is directly proportional to the pump rotation speed, so the injection timing is delayed the most when starting the engine, resulting in poor startability. Ta.

The present invention was developed with the aim of solving these conventional problems.In addition to the first passage that connects the feed pump discharge port and the pump chamber, the present invention has a first passage that connects the feed pump discharge port and the timer piston. By providing a second passage communicating with the chamber and further providing a valve that closes the first passage and opens the second passage at the time of starting, it is possible to obtain a starting advance angle.

Hereinafter, the present invention will be explained based on the drawings.

3 and 4 show an embodiment of the present invention. In addition, in this example, the conventional example (Fig. 1)
The same parts are given the same reference numerals.

To explain the configuration, another cylinder 21 is formed on the same axis as the cylinder 13, and this cylinder 2
1, a piston valve 22 is slidably inserted therein. Here, the pressure working chamber 23 formed on one side of the piston valve 22 and the pressure working chamber 15 of the timer piston 14 are opposed to each other, and these are connected to the sliding hole 2.
It is connected by 4. A spring 26 is housed in a chamber 25 formed on the other side of the piston valve 22 and acts on the piston valve 22.
5 is communicated with the low pressure side through a communication passage 27.

The piston valve 22 is integrally provided with a protrusion 28.
is formed and projected into the sliding hole 24. The proximal end of the protrusion 28 forms a large diameter part 28a, the middle forms a small diameter part 28b, and the distal end forms a large diameter part 28c. 29 is an O-ring.

A through hole 30 that opens into the pump chamber 4 is formed in the wall of the cylinder 21, and the piston valve 2
The pressure working chamber 23 and the pump chamber 4 are communicated with each other when the pump chamber 2 moves to the right in the figure.

On the other hand, a fuel passage 31 from the discharge port 2 a of the feed pump 2 extends to the wall of the cylinder 13 and opens at the circumferential surface of the sliding hole 24 .

Here, a first passage 32 is constituted by the right side of the sliding hole 24, the pressure operating chamber 23, and the through hole 30, and a second passage 3 is constituted by the left side of the sliding hole 24, as shown in the figure.
3 is composed.

Next, the action will be explained.

When the pump is stopped, the timer piston 14 is moved to the left in the figure by the spring 18, and is in a retarded state, and the piston valve 22 is moved to the right by the spring 26, and the base of the protrusion 28 of the piston valve 22 is moved to the right. The right side portion of the sliding hole 24 in the drawing is closed by the large diameter end portion 28a.

Therefore, at the time of startup, fuel discharged from the feed pump 2 flows from the fuel passage 31 through the left side portion of the sliding hole 24 in the figure into the pressure working chamber 15, and from the pressure working chamber 15 flows into the pump chamber 4 through the orifice 16a. leak. Here, pressure working chamber 1
Since 5 is a small, almost closed space, the internal pressure rises rapidly, causing the timer piston 14 to move to the left in the figure. Therefore, a sufficient starting advance angle can be obtained.

When the pump rotation speed is increased, the internal pressure of the pressure working chamber 15 further increases, but at this time, the piston valve 22
The piston valve 22 moves to the right in the figure due to the increase in pressure acting on the distal end surface of the protrusion 28, and the protrusion 28 moves to the right in the figure.
When the proximal large diameter portion 28a of 8 is removed from the sliding hole 24, the distal large diameter portion 28c closes the left side portion of the sliding hole 24 in the drawing.

Therefore, after starting, the fuel discharged from the feed pump 2 flows from the fuel passage 31 through the right side of the sliding hole 24 in the figure, into the pressure working chamber 23, and from this pressure working chamber 23 through the through hole 30 into the pump chamber. 4. It should be noted that once the piston valve 22 moves to the right side, the pressure receiving area increases, so it is held at the right position until the pump is stopped.

Therefore, after starting, the fuel is passed from the pump chamber 4 to the pressure working chamber 15 through the fuel introduction hole 16 with the orifice 16a.
The timer piston 14 is moved by the pressure of the fuel introduced into the engine, similar to the conventional method.

As described above, the advance angle characteristic is as shown in FIG. 5.

FIG. 6 shows another embodiment.

In this embodiment, the fuel passage 31 from the discharge port of the feed pump is extended to the wall of the cylinder 13,
Therefore, it branches into a first passage 34 and a second passage 35, the first passage 34 is opened to the pump chamber 4, and the second passage 34 is opened to the pump chamber 4.
While opening the passage 35 to the rotation working chamber 15,
A three-way solenoid valve 36 is interposed at the branching portion between the first passage 34 and the second passage 35.

This three-way solenoid valve 36 is energized, for example, from an engine key switch via a timer switch, and is energized for 2 to 3 seconds after startup to select the second passage 35 side, and thereafter select the first passage 34 side. You can configure it like this.

Incidentally, the advance angle characteristics including the starting advance angle may be electronically controlled by continuously changing the distribution ratio between the first passage 34 side and the second passage 35 side using the three-way solenoid valve 36. good.

As explained above, according to the present invention, at the time of starting, the fuel discharged from the feed pump is directly guided to the pressure operating chamber of the timer piston, thereby making it possible to advance the starting angle and improve starting performance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a distribution type fuel injection pump showing a conventional example, Fig. 2 is a line diagram showing advance angle characteristics of the conventional example, and Fig. 3 is a distribution type fuel injection pump showing an embodiment of the present invention. FIG. 4 is an enlarged sectional view of the main part of FIG. 3, FIG. 5 is a line diagram showing the advance angle characteristics in the same embodiment, and FIG. be. 2...Feed pump, 2a...Discharge port, 4...
...Pump chamber, 14...Timer piston, 15...
...Pressure operating chamber, 16a... Orifice, 18...
Spring, 22... Piston valve, 26... Spring, 31... Fuel passage, 32, 34... First
Passage, 33, 35...Second passage, 36...Three-way solenoid valve.

Claims (1)

[Claims for Utility Model Registration] (1) The fuel pressure of the pump chamber, through which fuel discharged from the feed pump is introduced, is introduced into the pressure operating chamber formed on one side of the timer piston through an orifice, and this fuel pressure is In an injection timing control device for a distribution type fuel injection pump, which controls injection timing by displacing a timer piston, in addition to the first passage connecting the discharge port of the feed pump and the pump chamber, the discharge port of the feed pump 1. An injection timing control device for a distribution type fuel injection pump, characterized in that a second passage is provided which communicates with the pressure working chamber, and further includes a valve that closes the first passage and opens the second passage at the time of startup. (2) Utility model registration claim No. 1, characterized in that the valve is a piston valve that operates in response to the pressure of fuel discharged from a feed pump and has a pressure-receiving area that is different between the initial position and the operating position. An injection timing control device for a distributed fuel injection pump according to item 1. (3) The injection timing control device for a distribution type fuel injection pump as set forth in claim 1 of the utility model registration claim, wherein the valve is a solenoid valve.