JPH0428904B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in delivery valves for fuel injection pumps.

As a conventional delivery valve, for example, the first
There is something like the one shown in the figure. In the figure, the delivery valve 2 mounted on the housing 1 of the injection pump has a holder 3 with an internal cavity 4, the opening 5 of the holder 3 being a valve seat with a valve hole 7 in the center. It is closed by member 6. Note that 8 is a sealing member.

A valve body 9 having a truncated conical sealing surface 10 is disposed within the internal cavity 4 of the holder 3,
A valve spring 11 is elastically biased so that its sealing surface 10 is seated on a tapered valve seat 12 of the valve seat member 6. Further, the valve body 9 includes a piston 13 that slides within the valve hole 7 and a stem 14 in which a plurality of vertical grooves 15 are formed.

The valve hole 7 communicates with a pressure chamber 18 on the head side of a plunger 17 that slides within a plunger barrel 16 of the injection pump.

Further, the internal space of the holder 3 is a high pressure pipe 1.
It communicates with the injection nozzle 20 via 9. In this way, the delivery valve 2 consists of the injection pump and the injection nozzle 2.
This is a valve device that opens and closes a fuel supply passage consisting of a valve hole 7 communicating with 0, an internal cavity 4 of the holder, and a high pressure pipe 19.

According to this configuration, when the fuel in the pressure chamber 18 is compressed by the rise of the plunger 17, this fuel pressure acts on the valve body 9 and causes the valve spring 11 to be compressed.
The valve opens against the elastic force of With this, the valve body 9
When the lower end of the piston 13 moves away from the valve seat 12 of the valve seat member 6, that is, when it lifts by L in FIG. 4 and is supplied to the injection nozzle 20 via a high pressure pipe 19.

Further, when the pressure in the pressure chamber 18 decreases after the pressure feeding stroke of the plunger 17 ends, the valve body 9 is pushed back by the pressure of the fuel remaining in the high-pressure pipe 19 and the elastic force of the valve spring 11. 9
When the lower end of the piston 13 passes the lower end of the valve seat 12 of the valve seat member 6, the high pressure pipe 19 and the pressure chamber 18 are cut off, and the sealing surface 10 of the valve body 9 passes the valve seat of the valve seat member 6. 12, that is, during the L stroke, the fuel in the high-pressure pipe 19 is sucked back to improve injection efficiency. (Refer to ``Engine'' on page 65).

However, in such a conventional delivery valve, when the lower end of the piston 13 of the valve body 9, which lifts in response to fuel pressure during the fuel pressure stroke, separates from the valve seat 12 of the valve seat member 6, the inside of the pressure chamber 18 The high pressure fuel obtained in
After the valve body 9 is opened, the pressure in the pressure chamber 18 and the pressure in the fuel passage leading to the injection nozzle 20 rise almost in the same way. Therefore, the rate of increase in the pressure of the injected fuel from the injection nozzle 20 depends on the rate of rise of the plunger 17, and especially when the pump rotation is fast and the rate of rise of the plunger 17 is high, the initial injection rate of fuel becomes high. However, there were problems in that the ignition delay in the combustion chamber increased, which not only increased NOx, HC, etc., but also increased engine noise.

The present invention has been made to eliminate these disadvantages of conventional devices, and includes a damper chamber whose volume contracts as the lift amount of the valve body increases, and a connection between the damper chamber and the injection pump for pressurizing fuel. A damping passage is formed that communicates with the pressure chamber via an orifice, and a damping passage is formed on the peripheral wall of the valve body to communicate with the downstream fuel supply passage at the beginning of the lift period as the valve body lift amount increases. a first groove having a small opening area and communicating the pressure chamber with the fuel supply passage on the downstream side during a predetermined period following the initial period; and a large opening after the predetermined period has elapsed. A delivery valve is provided, in which a second groove portion having an area and communicating the pressure chamber with a fuel supply passage on the downstream side is formed.

The present invention will be explained below with reference to embodiments shown in the drawings. Note that the same elements as those of the conventional device described above are given the same reference numerals, and the explanation thereof will be omitted.

In FIG. 2, a delivery valve 30 of the present invention is shown.
In particular, the valve body 31 is provided with a through hole to communicate with the internal space 4 of the holder 3 and the pressure chamber 18 of the injection pump, and one end thereof is a large diameter cylinder 33,
The other end is a damping passage 34 with a small diameter.
A lower end portion of a dump piston 36 as a fixed body is inserted into the cylinder 33 so as to be freely slidable. A damper chamber 37 is formed within the cylinder 33 . Further, an orifice 38 is disposed within the damping passage 34. Note that a communication hole 39 is formed in the spring seat 35 so that the internal space 4 and the communication hole 21 of the holder 3 communicate with each other. Further, a cylinder is provided at the upper part of the piston 13, and slides with the valve hole at the beginning of the lift period according to an increase in the lift amount of the valve body, and blocks communication between the pressure chamber 18 and the fuel supply passage on the downstream side. A tapered first groove portion 13a is formed in the lower part of the piston 13 and has a small opening area for a predetermined period following the initial period of the lift to communicate the pressure chamber 18 with the fuel supply passage on the downstream side. 13b is formed. Furthermore, the first groove portion 1
3b is formed, and the second groove 13c has a large opening area after a predetermined period of the lift has passed, and communicates the pressure chamber 18 with the fuel supply passage on the downstream side.

According to this configuration, before the plunger 17 starts to rise, the pressure chamber 18 and the damper chamber 37 are communicated with each other through the damping passage 34, so that both are maintained at the same fuel pressure. When the plunger 17 starts to rise and the fuel pressure in the pressure chamber 18 increases, the valve body 31 starts to lift against the elastic force of the valve spring 11. At this time, the volume of the damper chamber 37 is gradually reduced by the dump piston 36, so that the fuel in the damper chamber 37 tries to flow out into the pressure chamber 18, but this outflow is prevented by the orifice 38 in the damping passage 34.
As a result, the pressure of the fuel in the damper chamber 37 increases, and due to the elastic force with the valve spring 11 and the pressure in the damper chamber 37, the pressure of the fuel in the damper chamber 37 increases.
lift speed becomes slower.

Here, the orifice 38 in the damping passage 34
The diameter of the valve body 31 is set so that the lift speed of the valve body 31 becomes slow in the vicinity where the upper end of the piston 13 reaches the lower end of the valve seat 12 of the valve seat member 6 due to the action of the fuel pressure in the damper chamber 37. .

Therefore, the first part of the lower part of the piston 13 of the valve body 31
Since the upper end of the groove portion 13b of the first groove portion 13b is attached to the lower end of the valve seat 12 of the valve seat member 6, the first groove portion 13b
until the lower end of the valve seat 12 is separated from the lower end of the valve seat 12.
The flow rate of fuel that passes between the groove portion 13b and the inner diameter of the lower end of the valve seat 12 and is supplied from the pressure chamber 18 is restricted. This period is shown in graphs A and B in Figure 3b.
It is shown as.

Therefore, the pressure inside the pressure chamber 18 is higher than in the conventional example, as shown in the graph of FIG. 3a, and
The injection pressure from the injection nozzle 20 is lower than that of the conventional example, as shown in the graph of FIG. 3b. Therefore, since the injection nozzle 20 opens during the period from A to B, the initial injection rate becomes lower than in the conventional example, as shown in the graph of FIG. 3c.

Next, when the lower end of the taper 40 of the piston 13 separates from the lower end of the valve seat 12 of the valve seat member 6, there is no restriction on the flow of fuel from the pressure chamber 18, and the gap between the second groove 13c and the valve seat 12 is removed. Since a large opening area is ensured in between, after point B is passed, the high pressure of the fuel stored in the pressure chamber 18 before reaching point B is suddenly released into the high pressure pipe 19.

Therefore, as shown in the graph of Figure 3b,
The injection pressure from the injection nozzle 20 rises rapidly after point B, reaching a peak pressure higher than that of the conventional example. As a result, the injection rate becomes low at the beginning and becomes high later, as shown in the graph of FIG. 3c. Therefore, main injection (high injection rate) is performed after the ignition of the fuel injected first, so combustion is slow, which not only reduces NOx, HC, smoke, etc., but also reduces engine noise. do.

The operation of the delivery valve 30 of the present invention at the end of injection is similar to that of the conventional example described above.

In the above embodiment, the cylinder 33 is attached to the valve body 14.
A dump piston 3 that forms a cylinder and slides on the cylinder.
Although the damper chamber 37 is formed by the valve body 14
It is also possible to use the valve body as a piston and the fixed body such as a dump piston as a cylinder.In short, it is sufficient to form a damper chamber between the valve body and the fixed body and to allow them to slide freely and overlap each other.

As explained above, according to the present invention, the fixed body and the valve body are made to overlap each other so as to be able to slide freely by forming a tamper chamber therebetween, and the damper chamber and the pressure chamber of the injection pump are connected to the valve body. In addition to forming a damping passage passing through an orifice, the peripheral wall of the valve body is closed at the beginning of the lift period to sufficiently slow the lift speed, and then the valve is opened with a small opening area, and then the opening area is enlarged. Therefore, the fuel injection rate characteristics from the injection nozzle are low at the beginning and become high later. As a result, combustion becomes slow and NOx, HC,
Emissions such as smoke are reduced, and engine noise is also reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a conventional delivery valve, FIG. 2 is a longitudinal sectional view showing an embodiment of a delivery valve according to the present invention, and FIGS. 3 a, b, and c are a conventional example and an embodiment of the present invention, respectively. This is a graph comparing characteristics with an example. 3... Holder, 4... Internal cavity, 6... Valve seat member, 7... Valve hole, 11... Valve spring, 12... Valve seat, 13... Piston, 13a
...Cylindrical part, 13b...First groove part, 13c...
Second groove portion, 14... Stem, 16... Plunger barrel, 17... Plunger, 18... Pressure chamber, 19... High pressure pipe, 20... Injection nozzle,
30...Delivery valve, 31...Valve body, 34...
...damping passage, 36... dump piston (fixed body), 37... damper chamber, 38... orifice.

Claims (1)

[Claims] 1. A valve seat member interposed in a fuel supply passage that communicates the fuel pressure chamber of the injection pump with the injection nozzle, and a piston that slides within the valve hole of the valve seat member, and the valve seat member is operated by a valve spring. a valve body that can be seated from the injection nozzle side on a valve seat of a fuel injection pump, wherein a fixed body fixed to a downstream member of the valve body and the valve body are slidably superimposed on each other. A damper chamber is formed between the two, the volume of which contracts as the lift amount of the valve body increases, and a damping passage communicates the damper chamber with a fuel pressure chamber of the injection pump via an orifice. is formed in the valve body, and is provided on the peripheral wall of the valve body to supply fuel to the pressure chamber and the downstream side while sliding with the valve hole at the beginning of the lift period as the lift amount of the valve body increases. a cylindrical portion that blocks communication with the passage; a first groove portion that has a small opening area and communicates the pressure chamber with the downstream fuel supply passage during a predetermined period following the initial period; A delivery valve for a fuel injection pump, characterized in that a second groove portion is formed which has a large opening area after elapse of time and communicates the pressure chamber with the fuel supply passage on the downstream side.