JPS6125926A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To aim at preventing hesitation, etc. causing unsmooth acceleration, by disposing a variable orifice in an overflow pipe through which excess fuel is returned into a tank, and by controlling the variable orifice to decrease the flow passage area of the orifice with the decreasing of temperature of an engine. CONSTITUTION:In an overflow mechanism 20, a cylindrical screw 21 is at first screwed into a pump casing 15, and an annular part 22 formed in one end section of an overflow pipe 19 is fitted onto the outer periphery of the screw 21. Then, an annular groove 23 formed in the inner peripheral surface of the annular part 22 is always communicated with a hole 24 formed in the screw 21, and a valve element 25 is rotatably fitted in the screw 21. Further, a notch 25 formed in the lower end part of the valve element 25 is engaged with the hole 24 in the screw 21 so that the flow passage area of the hole 24, that is, the degree of constriction of the overflow mechanism 20 is changed in accordance with the degree of the engagement therebetween. At this time the degree of constriction of the overflow mechanism 20 is controlled such that the lower the temperature of the engine, the less the flow passage becomes.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a distributed fuel injection pump used, for example, in a diesel engine.

BACKGROUND OF THE INVENTION Fuel injection pumps of this type are normally configured to draw fuel from a fuel tank, supply it to a fuel injection nozzle, and return excess fuel that is not supplied to the fuel tank from an overflow pipe. Heretofore, in order to facilitate engine starting, particularly in cold regions, it has been known to incorporate a fuel injection pump with a cold start advance device or the like that advances the fuel injection timing. In other words, it advances the injection timing in the low engine speed range, and after starting,
As long as the engine rotates at low speed, it emits little white smoke (it runs smoothly).

In addition, as a device for adjusting the injection timing, for example,
There is one disclosed in Japanese Patent No. 8-118256.

Problems to be Solved by the Invention With conventional fuel injection pumps, the engine operates normally as long as it is operated in a low rotation range, but when racing or driving, the engine rotation speed increases beyond a certain level. In this case, the amount of advance in the fuel injection timing is insufficient, causing so-called hesitation in which acceleration is not performed smoothly.
There is a problem in that the riding comfort is impaired. The present invention was made with the aim of solving this problem.

Means for solving the problem The invention provides a variable throttle in the overflow pipe,
This variable throttle is characterized in that it is configured to reduce the flow path area as the engine temperature decreases.

Example The present invention will be explained below with reference to illustrated embodiments.

FIG. 2 shows a distribution type fuel injection pump, which, except for the overflow mechanism 20, has basically the same configuration as a conventionally known pump. The feed pump 1 is rotationally driven by a drive shaft 2, sucks liquid fuel in a fuel tank 16 from the direction of the arrow through a sedimenter (water drain) 17 and a filter 18, and supplies it into the pressure chamber 3. The plunger 4 is rotatable around the axis and moves forward and backward in the axial direction.
The fuel sucked in from the pressure chamber 3 through the pressure chamber 3 is fed under pressure to an injection nozzle (not shown) through a distribution passage 6 and a delivery valve 7. The injection nozzle opens depending on the pressure of the fuel, for example, and injects the fuel. Excess fuel that is not supplied to the injection nozzle is returned to the fuel tank 16 via an overflow pipe 19 connected to an overflow mechanism 20.

The plunger 4 is rotationally driven by a drive shaft 2, and moves forward and backward by engaging a face cam 8 and a roller 9 provided at the base. That is, the timing of fuel injection is determined by the engagement between these face cams 8 and rollers 9. The fuel injection timing is controlled by displacing the timer piston 10 and changing the position of the roller 9.

Note that the timer piston 10 receives fuel pressure in the pressure chamber 3 at its end face, and is displaced in accordance with this fuel pressure. Therefore, by changing the size of the throttle of the overflow mechanism 20 and changing the fuel pressure, the fuel injection timing can be controlled.

In order to prevent the fuel pressure in the pressure chamber 3 from becoming excessive, a pressure regulating valve 1 is installed in the middle of the discharge passage 11 of the feed pump 1.
2 is arranged. When the discharge pressure of the fuel increases as the rotational speed of the feed pump 1 increases, the excess fuel opens the pressure regulating valve 12 and the suction passage 1 of the feed pump 1 releases the excess fuel.
Reflux to the side.

FIG. 1 fa), (bl shows the overflow mechanism 20.

The cylindrical screw 21 is screwed onto the pump casing 15, and an annular portion 22 formed at the end of the overflow pipe 19 is fitted onto the outer periphery of the screw 21.

An annular groove 23 formed on the inner circumferential surface of this annular portion 22 is always in communication with a hole 24 formed in the screw 21. The valve body 25 is rotatably fitted into the screw 21. A notch 26 formed at the lower end of this valve body 25 is connected to the screw 2.
1, and depending on the degree of engagement,
The flow path area of the hole 24, that is, this overflow mechanism 20
The size of the aperture changes. A seal ring 27 is provided on the inner circumferential surface of the screw 21 to maintain liquid tightness between the screw and the valve body 25.

The throttle of the overflow mechanism 20 is configured such that the flow path area becomes smaller as the temperature of the engine becomes lower. For this purpose, various configurations are possible, but in this embodiment, as shown in FIGS. 3 and 4, the restriction is changed by a thermowax 40 attached to the outside of the pump casing 15. This thermowax 40 expands and contracts depending on the temperature of the cooling water. The thermowax 40 is connected via a pin 41 to one end of a lever 42 rotatably supported by the casing 15, and the other end of this lever 42 is connected to an arm 43 of the valve body 25.

The other end of the first lever 42 is also connected to the adjusting lever 30 of the governor mechanism. i.e. thermowax 4
0 and 42 are conventionally known low-temperature increase mechanisms. When the temperature of the cooling water decreases, the thermowax 40 contracts and the lever 42 is rotationally displaced in the direction of arrow B in FIG. 3, which causes the arm 43 to rotate (FIG. 4). The flow path area of the overflow mechanism 20 becomes smaller.

A spill boat 31 is bored on the base side of the plunger 4, and a spill ring 32 that can open and close the spill boat 31 is disposed.

Therefore, when the spill boat 31 is released from the spill ring 32 when the plunger 4 moves forward, the fuel starts to flow back from the spill boat 31 into the pressure chamber 3, and the injected fuel stops. The position of this spill ring 32 is adjusted by moving back and forth an adjustment rod 34 that comes into contact with a control lever 33. It is done by.

Since the present embodiment has the above-described configuration, when the engine temperature is relatively high, the flow path area of the throttle of the overflow mechanism 20 is large, and therefore the timer advance angle characteristic as shown by the broken line C in FIG. 5 is obtained. Therefore, the fuel injection timing is relatively late. On the other hand, when the engine temperature is relatively low, the flow path area of the throttle of the overflow mechanism 20 becomes small, and the pump internal pressure becomes high. Therefore, the timer advance characteristic becomes as shown by the solid line in Fig. 5, and the fuel injection timing becomes relatively early, and even if the engine speed increases, white smoke is not emitted. Hesitation is prevented and vehicle drivability is improved. In addition, the dashed-dotted line E shows the advance angle characteristic at the time of conventional starting. That is, in the conventional device, the amount of timer advance changes from the dashed-dotted line E to the broken line C as the engine speed increases.

As described above, in this embodiment, the fuel injection timing is advanced not only when the engine is cold or when idling, but also throughout the entire range of engine speed. Therefore, even when racing immediately after starting,
There is no white smoke like before. Furthermore, since the amount of overflow is small due to the throttling of the overflow mechanism 20, less fuel is replenished from the fuel tank 16 into the pump, and the fuel inside the pump is kept at a relatively high temperature. The sliding characteristics are also improved.

Furthermore, even if the fuel turns into wax and becomes clogged in the filter 18 or the like, it will take time for the fuel in the pump to become empty, reducing the possibility of fuel stalls.

As described in the detailed description of the invention, according to the present invention, white smoke is no longer emitted even when the engine speed increases in cold weather, and the drivability of the vehicle is improved by preventing fatigue. .

[Brief explanation of the drawing]

FIG. 1 fal is a cross-sectional view showing the overflow mechanism provided in the embodiment device of the present invention, FIG.
2 is a sectional view showing the embodiment device, FIG. 3 is a side view showing the mechanism for driving the valve body of the overflow mechanism, and FIG. 4 is the valve body of the overflow mechanism. FIG. 5 is a graph showing changes in the timer advance amount with respect to engine speed. 16-fuel tank, 19-overflow vibe, 20-overflow mechanism. Figure 1 Figure 5

Claims (1)

[Claims] 1. In a fuel injection pump that sucks fuel from a fuel tank and supplies it to a fuel injection nozzle, and recirculates surplus fuel that is not supplied to the fuel tank from an overflow pipe, a variable throttle is provided in the overflow pipe, and this throttle is located at a low engine temperature. A fuel injection pump characterized by having a flow path area that is as small as possible.