JPH0364663A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To simplify structure of a delivery valve mechanism and to reduce capacity of a delivery valve chamber by a method wherein a first valve body moved in an opening direction by means of fuel fed with a pressure and a second valve body the throttle hole of which is opened during the generation of reverse flow fuel are provided, and a single spring is located between the two valve bodies. CONSTITUTION:When operation to feed fuel with a pressure is started through drive of a plunger by means of an engine, a first valve body 13 is moved upward against a spring 22 by means of forcedly fed fuel. By separating a taper part 131 of the valve body 13 from a valve seat 12, high pressure fuel of a plunger chamber 11 is fed in a delivery valve chamber 15, and high pressure fuel in the delivery pressure chamber 15 is injected through a fuel passage 161 and a fuel hole 17. In a fuel forced feed process described above, a second valve body 19 is closed through the force of a spring 22, and when a fuel reverse flow is generated by means of an injection valve, by exerting reverse flow fuel on the second valve body 19 through a throttle hole 18, the valve body 19 is opened against the spring 22, and reverse flow fuel is returned to the plunger chamber 11.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention supplies injected fuel to fuel injection valves set corresponding to each of a plurality of cylinders of an engine in synchronization with the rotation of the engine. Regarding fuel injection pumps.

[Prior Art] A fuel injection pump that supplies fuel to fuel injection valves set in each cylinder of an engine has a first valve body that acts, for example, when pumping fuel, and a valve body that is opposite to the first valve body. and a second valve body that acts in the direction of the discharge valve mechanism. Then, the first valve body is moved by the pressurized fuel generated by the plunger mechanism driven in synchronization with the rotation of the engine, and the valve body is opened to supply the pressurized fuel to the fuel injection valve. Further, the second valve body is opened by the backflow fuel from the injection valve, so that the backflow fuel is returned.

For example, such a fuel injection pump is disclosed in Japanese Unexamined Patent Publication No. 56-115849. The fuel injection pump disclosed herein includes a snapper, a valve, a spring, a valve guide, etc. that maintains a constant residual pressure in the discharge valve chamber in order to prevent negative pressure in the fuel discharge valve chamber and injection pipe. parts and
The discharge valve itself has a discharge valve spring that opens and closes it, and the number of component parts has increased, particularly the quality of the discharge valve has increased, and the pumping efficiency has decreased, which has become a major obstacle to increasing the pressure.

To provide a fuel injection pump that can reliably prevent secondary injection, further simplify its configuration sufficiently, and reduce the number of component parts so that it can be made smaller. It is something.

[Means for Solving the Problems] The fuel injection pump according to the present invention includes a first valve body driven by pressurized fuel generated in synchronization with engine rotation, and a movement direction of this valve body. A second valve body is disposed coaxially opposite to the fuel injection valve, and is set in a constricted portion of the fuel pipe communicating with the fuel injection valve, and a single valve body is provided between the first and second valve bodies. A spring is interposed therebetween, and this single spring applies a force in the closing direction to each of fRl and the second valve element.

[Problems to be Solved by the Invention] [Operation] The present invention has been made in view of the above points, and has a fuel injection pump configured as described above. , and furthermore, in synchronization with the rotation of the engine, the bra adjuster 1. : The pumped fuel generated by the first
act on the first valve body, move this first valve body against a single spring, feed the pumped fuel into the discharge chamber, force the fuel from the discharge chamber to the fuel injection valve, and inject the fuel. The action will now be executed. Also, when fuel starts to flow backwards from the direction of the fuel injection valve, the second valve body is moved against the single spring by this backflow fuel pressure, and the fuel pressure is reduced through this valve body. Since the plunger is returned to the lowered position, negative pressure is generated in the discharge chamber and secondary injection is reliably prevented. In this fuel injection pump, the first and second valve bodies constituting the discharge valve mechanism are controlled by a single spring, and the configuration is simplified and the discharge pressure chamber is controlled by a single spring. The parts can be made smaller and the maximum injection pressure can be increased easily.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

(A) in Figure 1 shows its cross-sectional structure.
A plunger (not shown) is installed in the plunger chamber 11, and this plunger is reciprocated by a drive shaft driven by the rotation of an engine (not shown) to perform the function of pumping fuel. This plunger chamber 1
1 includes a valve seat 12 coaxially communicating with the valve seat 12.
A first valve body 13 serving as a discharge valve is set in the cylindrical hollow portion of the valve seat 12.

That is, when the fuel pressure within the plunger chamber 11 becomes high, the first valve body 13 is moved in a first direction upward in the figure by the pressure. And, between the tapered portion 13t of the first valve body 13 and the valve seat 12,
A discharge valve chamber 15 formed inside the valve holder 14 is opened as the first valve body 13 moves in the first direction.
Then, high pressure fuel supplied from the plunger chamber 11 is introduced.

Here, as shown in FIG. 1B, the first valve body 13 has a structure in which a plurality of grooves 133 for passing fuel are formed on the outer circumference, and the first valve body 13 1, fuel from the plunger chamber is introduced through this groove 33.

The first valve body 13 has a discharge valve chamber 1 in the valve holder 14.
A cylindrical guide 132 with an open upper side in the figure is formed so as to extend coaxially within the guide 5 .

Further, a valve holding member 16 is attached to a position of the discharge valve chamber 15 facing the first valve body 13 . The valve holding member 16 is inserted and fixed into the hollow portion of the guide 132, and the first valve body (3) is movable in the axial direction along the valve holding member 1B.

A fuel passage 181 is formed in the central axis portion of the valve holding member 1G, and this passage 161 is further communicated with the discharge valve chamber 15 through passages 162 and 163. This fuel passage 181 is communicated with an injection pipe of a fuel injection valve (not shown) via a fuel hole 17 formed in the valve holder i4.

A throttle hole 18 communicating with the fuel passage 17 is opened at the end of the valve holding member 1B in the direction of the first valve body 18. The opening formed by this throttle hole 18 is used as a valve seat.
A spherical second valve body 19 is set in this valve seat portion.

A valve guide 20 is provided opposite to the second valve body 19, and a shim 21 is provided between the valve guide 20 and the first valve body 13 as appropriate.
A single spring 22 is interposed via. That is, the first valve body 13 moves in a first direction upward in the figure against the spring 22 while the high pressure fuel in the plunger chamber 11 is set, and the second valve body 19 moves in a first direction upward in the figure. When the pressure in the valve chamber 15 is higher than that in the spring chamber 23, it is moved in the second direction, which is the downward direction in the figure, against the spring 22, and the throttle hole 1B is moved. The spring chamber 23 in which the spring 22 is set is communicated with the plunger chamber 11 via a passage 24.

That is, in the fuel injection pump configured as described above, when the plunger is driven by the engine to perform an operation of pumping fuel, the first valve body 13 is moved by the spring 22 in the first direction due to the pressure of the pumped fuel. The tapered portion 131 of the valve body 13 separates from the valve seat 12, and the high-pressure fuel in the plunger chamber 11 flows into the discharge valve chamber 15.
will be sent to. And this discharge pressure chamber 15
The high-pressure fuel is fed under pressure to the injection pipe of the fuel injection valve through the fuel passage 181 and the fuel hole 17, and the fuel is injected into a predetermined cylinder of the engine.

When such a fuel pressure feeding stroke is completed, the plunger chamber 1
1, the pressure of the first valve body 13 is lowered by the spring 22.
During this return operation, the tapered portion 131 comes into contact with the valve seat 12, and the valve is sealed airtight in the closed state.

The second valve body 19 is closed by a spring 22 during such a fuel pressure feeding stroke, and when a backflow of fuel occurs from the injection valve, this backflow fuel flows into the throttle hole 18.
The spring 22 acts on the second valve body 19, and the spring 22
The valve moves in the second direction (downward) against the pressure and opens the valve. Therefore, the backflow fuel is returned from the spring chamber 23 to the plunger chamber 11 via the passage 24.

That is, the reflected wave from the injection valve becomes smaller as the second valve body 19 is opened and the backflow fuel is returned to the plunger chamber 11, thereby preventing the occurrence of secondary injection. Also, by selecting the diameter of the throttle hole L8 or the valve opening pressure that applies the valve opening pressure to the second valve body 19, f
It is possible to limit the degree of pressure drop during the time from when the valve body 19 of f12 opens until it closes, and cavitation erosion can be prevented without making the pressure in the discharge pressure chamber 15 and the injection pipe negative. executed effectively.

Here, the valve opening pressure of the second valve body 19 can be easily adjusted by adjusting the thickness of the shim 21, for example.

In such a fuel injection valve, the opening pressure of the discharge valve is set by the first and second valve bodies 13 and 19, for example, as follows. First, the first valve body 13 is designed to prevent the first valve body 13 from being lifted by a spill wave returned from a plunger that communicates the plunger chamber 11 with an injection pump corresponding to another cylinder when the plunger chamber 11 is not in operation. ,
- 2Kg/e12 to 30Kg/cm'' is set in the membrane.The second valve body 19 is set lower than the opening pressure of the fuel injection valve (not shown) to prevent the pressure inside the fuel pipe from becoming negative. In addition, the opening pressure of the first valve body (3) is set higher than that of the first valve body (3).

By changing the seat diameters of the first and second valve bodies 13 and 19, the ratio of the valve opening pressures can be changed from 7 to 20 times, and with a single spring 22, the required The setting control of the valve opening pressure becomes possible.

The opening pressure of the second valve body 19 is set by inserting the first valve body 13 into the valve seat 12, and then applying the spring 22 and the valve guide 20.
, the second valve body 19, the valve holding member 16, and the valve holder 14 are assembled, and the valve holder 14 and the valve seat 12 are in close contact with each other as shown in the figure, and pressure is applied from above the valve holder 14. By adding , complete measurement is possible.

In this measurement state, the valve opening pressure of the second valve body 19 is adjusted by adding the number of shims 21.

Note that this adjustment work also adjusts the valve opening pressure of the first valve body 13, so the adjustment of the valve opening pressure only needs to be done once. In the case of a discharge valve mechanism that uses two springs, adjustments must be made for each spring, which requires a complicated process, and the variation in adjustment inevitably increases by one point, resulting in unevenness. However, if the discharge valve mechanism is configured with a single spring 22 as shown in the embodiment, variations in adjustment are less likely to occur, and uneven amounts can be easily fixed. You can set it smaller.

In the fuel injection pump configured in this manner, the effect of preventing cavitation erosion is effectively exhibited in addition to the secondary injection, and at the same time, the capacity of the discharge valve chamber can be set to be small. Therefore, since only one spring is used, costs can be effectively reduced, and the pressure can be increased easily, making it easier to adjust the valve opening pressure. It becomes possible to configure a high-performance fuel injection pump.

FIG. 2 shows another embodiment, in which a fuel passage 30 is formed in a slight gap between the first valve body 13 and the non-retaining member t6. . The rest of the structure is the same as that of the embodiment shown in FIG. 1, so the same reference numerals are given and the explanation thereof will be omitted.

By forming the passage 30 in this way, the residual pressure in the injection pipe of the injection valve in the high speed range can be set close to the valve opening pressure of the second valve body 19, and in the low speed range, the residual pressure in the injection pipe of the injection valve can be set close to the opening pressure of the second valve body 19. By leaking fuel, the residual pressure can be kept low.

FIG. 3 shows the relationship between the pump rotation speed and the fuel injection material. When the residual pressure is constant, it is indicated by the broken line A, whereas when the passage 30 is formed, it is indicated by the solid line B. As shown in , the injection amount decreases in the low speed range. As shown in FIG. 4, when the passage 30 is formed, the opening speed of the rack at high and low speeds of the governor can be made smaller as shown in b when the passage 30 is formed, compared to a when the residual pressure is constant. This provides a property that facilitates

〔Effect of the invention〕

As described above, according to the fuel injection pump according to the present invention,
The discharge valve mechanism can be configured with a simple configuration using a single spring, and the discharge valve chamber can be configured with a small capacity. In this state, negative pressure is generated from the discharge valve to the injection valve, and Injection can now be prevented and the maximum injection pressure can be easily increased. Therefore, the attachment to the engine can be easily set, and the fuel injection characteristics can also be set stably, which can have a great effect on stabilizing the engine characteristics.

[Brief explanation of drawings]

(A) of FIG. 1 is a cross-sectional configuration diagram illustrating a fuel injection pump according to an embodiment of the present invention, (B) of the same figure is a cross-sectional view corresponding to the b-b line of FIG. The figure is a cross-sectional configuration diagram for explaining another embodiment of the present invention, and FIGS. 3 and 4 are diagrams for explaining the operating characteristics of the above embodiment, respectively. 11...Plunger chamber, 12...Valve seat, 1
3... First valve body (discharge valve), 14... Pulp holder, 15... Discharge seat chamber, 16... Valve holding member, 17... Fuel hole, 18... Throttle hole , 19... Second valve body, 22... Spring (single), 30... Fuel passage.

Claims (1)

[Claims] A first valve body configured to be linearly movable and moved in a first direction by pressurized fuel generated in synchronization with engine rotation; while being moved in the first direction;
a discharge valve chamber to which the pressurized fuel is set to be supplied; a fuel hole that communicates with the discharge valve chamber and guides high-pressure fuel set by the pressurized fuel into the discharge valve chamber to the fuel injection valve; and a fuel hole that communicates with the fuel hole. a throttle hole coaxially formed in the fuel hole located in the first moving direction of the first valve body and formed in a fuel hole communicating with the injection valve; a second valve body that is moved in a second direction opposite to the first direction to open the throttle hole by the fuel pressure of the second valve body, and the second valve body and the first valve body A single spring is interposed between the valve body and the valve body to apply a biasing force to the second valve body in a first direction and to apply a biasing force in a second direction to the first valve body. and fuel injection pump.