JPH0670416B2 - Fuel injection pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection pump.

(Prior Art) In a diesel engine, generally, during low speed / low load operation such as idle operation, combustion is rapidly performed by a large amount of evaporated fuel during the ignition delay period of the fuel spray during this period, and the cylinder of the engine There is a problem that the internal pressure rise rate rises sharply and large combustion noise is generated.

As one method to solve this, it is possible to suppress the pressure rise rate of the in-cylinder pressure by performing slow combustion at low speed and low load, and as a concrete means thereof, for example, Japanese Utility Model Publication No. 51-23778. As disclosed, in addition to the metering reed, a vertical groove extending in the axial direction of the plunger is formed in the plunger, and this vertical groove is communicated with a relief amount adjusting valve provided on the barrel side, and this vertical groove is provided during the compression stroke. It is known that a part of the fuel is gradually discharged in a throttled state to reduce the fuel injection rate to realize slow combustion and thereby suppress the pressure increase rate in the cylinder of the engine.

However, in the case of this known example, although the combustion noise reduction effect can be obtained by suppressing the pressure rise rate, the throttle outflow action by the relief amount adjusting valve is performed from the beginning of the fuel pressure stroke. The fuel pumping start timing is different between the low speed operation and the high speed operation of the engine due to the difference in the outflow resistance due to the viscosity and inertia of the fuel (that is, where the fuel outflow resistance is smaller during low speed operation than during high speed operation). The fuel is smoothly squeezed out from the
As a result, the fuel pumping start timing is delayed compared to during high-speed operation). Therefore, correspondingly, when the engine load is the same, the fuel injection amount defined by the fuel pressure feed start timing and the fuel pressure feed end timing by the lead also changes according to the engine speed. Become.

On the other hand, since the fuel injection amount is defined by the lead as described above, the variation in the processing accuracy of the lead is directly expressed as the variation in the fuel injection amount.

As described above, the fuel injection pump having the structural characteristic that the fuel injection amount increases and decreases depending on whether the engine speed is high or low and the lead processing accuracy is good or bad is not a problem when it is applied to a single cylinder engine. However, when this is applied to a multi-cylinder engine, it is difficult to make the fuel injection amount uniform among the cylinders because the manner of changing the fuel injection amount is complicated. The current situation is that it cannot be applied to engines.

(Object of the Invention) The present invention is intended to solve the problems pointed out in the above-mentioned prior art, and maintains the fuel pumping start timing constant regardless of the engine speed, and also during low load operation. The purpose of the present invention is to provide a fuel injection pump that can be applied to a multi-cylinder engine by reducing combustion noise in the above.

(Means for Achieving the Purpose) As a means for achieving the above object, the present invention applies fuel in a pressurizing chamber formed on the top surface of the plunger by reciprocating the plunger in the barrel. On the outer peripheral surface of the head of the plunger, a slanted groove-shaped lead communicating with the top surface of the plunger is formed, while enabling pressure and pressure feeding.
In the fuel injection pump, which adjusts the fuel injection amount by adjusting the communication timing between the lead and the barrel port formed in the barrel by appropriately rotating the plunger and the barrel appropriately, In the state between the top surface and the lead, and in the circumferential direction of the plunger, the portion corresponding to the barrel port during low load operation of the engine is formed so as to communicate with the lead and is in superposed communication with the barrel port. A throttle outflow passage portion that acts so as to let a part of the pressurized fuel in the pressure chamber flow out to the barrel port side in a throttled state is provided, and the edge of the throttle outflow passage portion on the plunger top surface side and the plunger top surface are provided. Is set to be larger than the opening size in the axial direction of the plunger of the barrel port by a predetermined stroke.

(Operation) According to the present invention, by the above means, (1) during the fuel pressure feeding stroke of the plunger, for example, even when the relative rotational position between the plunger and the barrel is set to a position corresponding to the low load operation. , The barrel port and the throttle outflow passage are not in communication with each other within a predetermined stroke range from the time when the barrel port passes the position corresponding to the top surface of the plunger, and the fuel pressure start timing is independent of the engine speed. It is always maintained at a fixed time by the plungeer top surface.

(2) The fuel injection amount is regulated by the plunger stroke between the plunger top surface and the reed because the start time of fuel pumping is always kept constant by the plunger top surface, and the influence of the plunger speed on the fuel injection amount is affected. It is eliminated, and the control thereof, especially the control of the equalization of the injection amount between the cylinders becomes easy, and the like.

(Embodiment) FIG. 1 shows a fuel injection pump Z for an internal combustion engine according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a pump main body having an integral mounting flange, and 2 is a pump main body 1. The barrel 2 is fitted and fixed, and a barrel port 10 (shown by a chain line) having a circular cross section is formed on one side of the barrel 2.
In addition, a plunger fitting insertion hole 18 is formed at the axial center of the barrel 2 so as to communicate with the barrel port.
The plunger 3 is inserted into the plunger insertion hole 18 so as to be relatively rotatable and slidable. The plunger 3 is attached to the spring force of the plunger spring 5 and a fuel cam (not shown).
By reciprocating in the axial direction due to the cam action of the fuel, the fuel sucked into the pressurizing chamber 16 formed on the plunger top surface 3b is pressurized, and this is injected through the delivery valve 6 into the engine (not shown). The fuel is supplied to an injector (not shown) provided in the cylinder.

Further, in FIG. 1, reference numeral 7 is a plunger rotating wheel that is attached to the plunger 3 in a circumferentially engageable manner, and the plunger 3 is meshed with the plunger rotating wheel 7 by a metering operator 8. By appropriately pushing and pulling the rack gear 9, the rack gear 9 is relatively rotated in the barrel 2 to perform a predetermined metering action. That is,
The outer peripheral surface 3c of the head 3a of the plunger 3 is shown in FIGS.
As shown in the drawing, oblique groove-shaped leads 11 are formed over approximately half the circumference thereof, being appropriately separated from the top surface 3b. The lead 1 is communicated with the top surface 3b of the plunger 3 through a communication hole 12 formed in the axial center of the plunger 3. Therefore, by rotating the plunger 3 relative to the barrel 2, the relative communication timing between the lead 11 of the plunger 3 and the barrel port 10 of the barrel 2 is changed to adjust the closing period of the barrel port 10. The fuel injection amount is adjusted by. A metering mechanism comprising such a combination of the barrel port 10 and the lead 11 which is communicated with the barrel port 10 is conventionally known. In this embodiment, in addition to this, the present invention is applied to the plunger 3 described above. Outer peripheral surface 3c
In addition, the lead 11 is located near the top surface 3b.
A rectangular slide portion 14 having a small depth is formed in communication with the groove 11, and a portion surrounded by the square slide portion 14 and the inner surface of the plunger fitting insertion hole 18 of the barrel 2 is used as a throttle outflow passage portion 13. The square slide portion 14 may be formed in a flat surface or may be formed in a curved surface as appropriate. The throttle outflow passage portion 13 is formed at a position corresponding to the barrel port 10 of the barrel 2 at the plunger rotation position in the low load operation area including the idle operation area in the circumferential direction of the plunger (see the chain line in FIG. 2). The positions corresponding to 10A, 10B, and 10C) are set to be not in communication with the barrel port 10 (10D shown by the chain line in FIG. 2) at the time of starting with low rotation. The position 13b at the end of the outflow passage portion 13 in the direction of rotation of the plunger is determined so as to be in a non-communication state with the barrel port 10 at the time of cold start.

In the direction of the plunger axis, the lower edge of the barrel port 10 is squeezed out from the state in which the upper edge of the barrel port 10 is aligned with the plunger top surface 3b as shown by the chain line 10A in FIG. Plunger stroke L ₁ exists until it matches the upper edge 13a of the passage portion 13, and between the position of the broken line 10B and the barrel port 10 overlaps with the lead 11 as shown by the broken line 10C. Is throttled so that the plunger stroke L ₂ exists
The formation position of is set.

The passage area of the throttle outflow passage portion 13 is
The size is set so that a part of the pressurized fuel in the pressurizing chamber 16 can be gradually discharged toward the barrel port 10 side in a state where 13 is superposed on the barrel port 10 of the barrel 2.

According to the fuel injection pump Z configured as described above, in the low load operation region of the engine, the barrel port 10 as shown by a chain line 10A in FIG.
Is started by the outer peripheral surface 3c of the plunger 3, the fuel pumping action is started, and the fuel pumping action without throttle outflow is continued during the period corresponding to the plunger stroke L ₁ , but the barrel port 10 is throttled outflow. When communicating with the passage portion 13, a part of the pressurized fuel flows out to the barrel port 10 side through the throttle outflow passage portion 13 in a throttled state, and the increase rate of the fuel pressure in the pressurizing chamber 16 is reduced. This squeezing outflow action is continued during the period corresponding to the plunger stroke L ₂ until the barrel port 10 communicates with the lead 11.
The fuel pumping action ends when 10 communicates with lead 11 in a superposed manner.

As described above, in the fuel injection pump Z, the fuel pumping start timing is fixedly defined by the plunger top surface 3b and is not affected by the engine speed, that is, the plunger speed. Therefore, the fuel injection amount defined by the fuel pumping start timing by the plunger top surface 3b and the fuel pumping end timing by the lead 11 is maintained at a substantially constant amount at the same load position (same rack position) regardless of the engine speed. To be done. Further, at this time, the fuel injection amount slightly changes depending on the processing accuracy of the lead 11, but since the increase / decrease amount of the fuel injection amount due to the quality of the processing accuracy can be grasped quantitatively, its adjustment is easy, and therefore the fuel Even when the injection pump Z is applied to a multi-cylinder engine, the non-uniformity of the fuel injection amount among the cylinders can be relatively easily corrected, and the fuel injection pump Z can be applied to the multi-cylinder engine.

Also, in the latter half of the fuel pressure stroke, the throttle outflow passage
A part of the fuel is squeezed out by 13 and the fuel pressure in the pressurizing chamber 16 is maintained at a relatively low pressure. Therefore, the fuel injection from the injector (not shown) is performed at a relatively low pressure and slowly over a long period of time, so that the combustion of the air-fuel mixture in the cylinder becomes slow, a sudden increase in the cylinder pressure is prevented, and the combustion of the engine is prevented. Noise will be effectively and reliably prevented.

On the other hand, when the engine is started, the barrel port 10 and the throttle outflow passage portion 13 are not communicated with each other, so that the fuel injection amount is secured and the engine can be started.

(Effect of the Invention) The present invention makes it possible to pressurize and pump fuel in the pressurizing chamber formed on the top surface of the plunger by reciprocating the plunger in the barrel, while An oblique groove-shaped lead communicating with the top surface of the plunger is formed on the outer peripheral surface, and the plunger and the barrel are appropriately rotated relative to each other to adjust the communication timing between the lead and the barrel port formed in the barrel. In the fuel injection pump that adjusts the fuel injection amount by doing, in the portion corresponding to the barrel port between the top surface of the plunger and the reed, and at the time of low load operation of the engine in the plunger circumferential direction, In a state in which it is formed in communication with the lead and is in polymerization communication with the barrel port, a part of the pressurized fuel in the pressurizing chamber is squeezed to the barrel port side. In addition to providing a throttle outflow passage portion that acts so as to allow the water to flow out in a state, a distance between the edge of the throttle outflow passage portion on the plunger top surface side and the plunger top surface is set to be more predetermined than the opening size of the barrel port in the plunger axial direction. The feature is that only the stroke is set larger.

Therefore, according to the fuel injection pump of the present invention, (1) during the fuel pressure-feeding stroke of the plunger, even if the relative rotational position between the plunger and the barrel is set to a position corresponding to the low load operation. In the range of a predetermined stroke from the time when the barrel port passes the position corresponding to the top surface of the plunger, the non-communication state between the barrel port and the throttle outflow passage portion is secured, and the fuel pressure start timing is related to the engine speed. No, it is always maintained at a fixed time by the plunger top surface. (2) Since the fuel pumping start time is always kept constant by the plunger top surface, the fuel injection amount is the plunger stroke between the plunger top surface and the reed. The effect of the plunger speed on the fuel injection amount is eliminated by the control, especially the control of the injection amount between the cylinders. (3) The injection rate decreases due to the throttled outflow action of the fuel from the outflow passage portion during low-speed / low-load operation such as idle operation, and the injection period increases and combustion noise is reduced. Therefore, the effect that it can be applied to a multi-cylinder engine can be obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a fuel injection pump according to an embodiment of the present invention, FIG. 2 is an enlarged view of a II portion of FIG. 1, and FIG. 3 is a II portion of FIG.
It is an I-III cross-sectional view. 1 …… Pump body 2 …… Barrel 3 …… Plunger 9 …… Measuring rack 10 …… Barrel port 11 …… Lead 12 …… Communication hole 13 …… Throttle outflow passage section 14 …… Square sliding section 16 …… Addition Pressure chamber

Claims (1)

[Claims] 1. A fuel in a pressurizing chamber (16) formed on a top surface (3b) of the plunger (3) is pressurized by reciprocating the plunger (3) in the barrel (2). The plunger (3) has a head (3a) having an oblique groove-shaped lead (11) communicating with the top surface (3b) of the plunger (3) on the outer peripheral surface (3c) of the plunger (3). (3) and the barrel (2) are appropriately rotated relative to each other to appropriately move the lead (11).
A fuel injection pump for adjusting the fuel injection amount by adjusting the communication timing between the barrel port (10) formed in the barrel (2) and the barrel port (10), the top surface (3b) of the plunger (3). ) And the lead (11) and in the circumferential direction of the plunger in a portion corresponding to the barrel port (10) during low-load operation of the engine, the barrel port (10) is formed in communication with the lead (11). A throttle outflow passage portion (13) is provided which acts so as to allow a part of the pressurized fuel in the pressurization chamber (16) to flow out to the barrel port (10) side in a throttled state in a state of being polymerized and communicated with the valve. At the same time, the distance between the edge (13a) of the throttle outflow passage portion (13) on the plunger top surface (3b) side and the plunger top surface (3b) is determined by the opening dimension of the barrel port (10) in the plunger axial direction. Also a predetermined str Fuel injection pump, characterized in that the larger set by click L _1.