JPS5999060A - Injection rate controller for fuel injection pump - Google Patents

Abstract

PURPOSE:To reduce an initial injection rate and obtain smooth generation of heat in initial combustion by a method wherein a part of fuel in a high-pressure chamber defined at the end face of a plunger can be released into a pump chamber in accordance with an operating condition in the distributing supply type fuel injection pump. CONSTITUTION:Fuel in the pump chamber 5 is sucked from a suction port 12 into the high-pressure chamber 6A by the rotating and reciprocating motion of the plunger 7 while the fuel is pressurized and, thereafter, the high-pressure fuel is distributed to each fuel injection valves through a center hole 37, a distributing port 13 and a delivery valve 14. In such device, a groove 40, located between the suction port 12 and the distributing port 13 and surrounding the plunger 7, is formed. A fuel escape path 42, communicated with the groove 40 and the pump chamber 5, is formed while a variable section orifice 43 is interposed in the path 42. Further, the plunger 7 is formed with a communicating hole 41, communicating with the groove 40 between a predetermined divisions on the way of the advancing path of the plunger 7, into the radial direction thereof from the center hole 37.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection rate control device for a fuel injection pump such as a diesel engine.

- In diesel engines, the amount of fuel injection is variably controlled according to the engine speed and required output (load) (Nissan Motor Co., Ltd., 1980 technical manual "Diesel Enso/" published June 1973) P.

93-P, 106).

An example of such control means is a distribution type fuel injection pump as shown in FIG. 1, which is most widely put into practical use.

First, fuel is sucked from a pump body 1 by a feed pump 3 driven by a drive shaft 2 connected to an engine output shaft.

The fuel discharged from the feed pump 3 is supplied to the pump chamber 5 inside the pump housing 31 with the supply pressure controlled by the pressure regulating valve 4 .

The fuel in the pump chamber 5 lubricates the working parts and is simultaneously sent to the high-pressure GRA/TSU pump 6 through the suction boat 12.

The plunger 7 of this Bonpro is fixed to a cam disk 8 connected to a drive shaft 2, and is driven by the drive shaft 2 through two couplings in synchronization with the rotation of the engine.

The cam disk 8 has the same number of 7-eighth cams 9 as the number of engine cylinders, and each time the 7-eighth cams 9 ride over a roller 11 disposed on the low sill ring 10 while rotating, it reciprocates by a predetermined cam lift. do.

Therefore, the planter 7 reciprocates while rotating, and this reciprocating movement forces the fuel sucked from the suction boat 12 from the distribution boat 13 through the delivery nozzle 214 to an injection nozzle (not shown).

On the other hand, the amount of fuel to be injected is determined by the position of the control sleeve 16 that covers the cut-off boat 15 formed on the planter 7. For example, cut-off boat 15
When the opening of the plunger 7 passes the right end of the control sleeve 16 due to the rightward movement of the plunger 7, the fuel that had been pumped from the plunger melon chamber 6A to the distribution boat 13 passes through the cut-off boat 15 and is reduced to low pressure. Since the water is released into the pump chamber 5, the pressure feeding to the distribution boat 13 is completed.

Therefore, if the control sleeve 16 is displaced to the right relative to the plant gear 7, the fuel injection end time will be delayed and the fuel injection amount will be increased, whereas if the control sleeve 16 is displaced to the left, the fuel injection end time will be brought forward. This results in a decrease in the amount of fuel injected.

The control sleeve 16 is supported by a link lever device 19 that is interlocked with an accelerator pedal (not shown), and is displaced depending on the amount of depression. At the same time, the governor mechanism 18, which is driven by the rotation of the drive shaft 2, corrects and controls the link lever device 19 to increase or decrease the fuel injection amount in order to always maintain a constant engine speed corresponding to the accelerator opening.

This link lever device 191d, collector lever 21,
It consists of a tension lever 22, a start lever 23, and a start spring 24.

The collector lever 21 is rotatably supported by the bonphaunong 31 about a fulcrum B, and is pressed against a full-loaded, strong screw 26 by a compression spring 25 and remains stationary.

The tension lever 22 and the start lever 23 are rotatably provided on the collector lever 21 about a fulcrum A, and the tension lever 22 and the start lever 23 are connected to the collector lever 21 via a control shaft 27 as the control lever 20 rotates. A biasing force is applied to the tension spring 28 which increases and decreases depending on the direction, and this biasing force is applied via the start spring 24 to the start train/? -23, and presses the start lever 23 against a governor sleeve 18f of a governor mechanism 18, which will be described later.

The control sleeve 16 is supported by the start lever 23 via the /1-6-rusoyoi/) 18g.

Therefore, if the lever 20 is turned to increase the tension of the tension spring 28, the Te/7/Yo/lever 22 will rotate counterclockwise, pushing the start lever 23 via the start spring 24, and moving the lever 23 around the fulcrum A. the control sleeve 16 to the right to increase the fuel injection amount.

On the other hand, the governor mechanism 18 is built into the upper part of the injection pump main body, and the fly weight 18C is rotatable about the joint point 18d in the seven lie weight holder 18b which is integrally constructed with the gear 18a. It is labeled as. The flyweight holder 18b rotates according to the rotation of the drive shaft 2 transmitted via the 5th gear 18a)
When sliding and rotating around 18e, the flyweight 18c
It also rotates and expands around the junction point 18d under the rotational centrifugal force.

For example, if the rotational speed increases even though the accelerator opening does not change, the vana sleeve 18f fits into the gun shaft 18e and engages with the flyweight 18c, but the vana sleeve 18f is moved forward by the flyweight 18c. As the governor sleeve 18f moves forward, the start lever 23
The control sleeve 16 rotates around the fulcrum A against the pressing force of the start spring 24, and moves the control sleeve 16 to the left in the figure to reduce the fuel injection amount. Therefore, the engine speed decreases and converges to the engine speed corresponding to the accelerator opening.

Further, the fuel injection timing is controlled by rotating the low sill ring 10.

Specifically, when the 7-eighth cam 9 force of the cam disc 8 rides on the roller 11, fuel is injected, so for example, the low sill 10 is rotated in the opposite direction to the rotational direction of the cam disc 8.
By rotating , the time when the face cam 9 rides on the low 211 becomes earlier, so the injection time of the fuel relative to the engine crank angle becomes earlier.

For this purpose, Rollerly/button 0 is set to timer slide bin 2.
It is rotatably fitted to the timer piston 30 via 9.

The fuel pressure of the pump chamber 5 is introduced through a passage 33 to the high pressure chamber 32 at the end face of the timer piston 30 sliding in the cylinder 30A, and the low pressure chamber 34 on the opposite side is introduced to the feed pump 3.
The timer piston 30 is pushed back by the elastic force of the spring 350. Note that Figure 1 shows the axis of the timer piston/30 rotated 90 degrees, and in reality it is a low sill ring 10.
coincides with the tangential direction of rotation. Similarly, for convenience of explanation, the axis of the feed pump 3 is also shown rotated by 90 degrees in the same drawing.

Since the fuel pressure in the pump chamber 5 increases in proportion to the rotation speed of the feed pump 3, the timer piston 30 is pushed to the left as the engine rotation speed increases, and this causes the rotation of the cam disk 8 and It rotates the roller ring 10 in the opposite direction and acts to relatively advance the injection timing.

By the way, in this device, the injection rate (injection amount per unit crank angle) is uniquely determined by the plunger speed determined by the plunger diameter and the profile of the eight-axis cam 9, and the injection rate can be changed according to the operating conditions. do not have. For this reason, especially when this device is combined with a hole-type nozzle, the heat generation rate at the initial stage of combustion is increased, and NOx
There was a problem that the emission level and the noise level increased.

The present invention provides a fuel injection pump for a diesel engine in which a single plunger performs reciprocating motion while rotating, sucks fuel in a pump chamber from an intake port into a high chamber, and distributes it to each cylinder from a distribution port via a center hole. a group located around the plantar between the suction port and the distribution port and communicating with the pump chamber via a fuel relief passage;
A communication hole is provided from the center hole perpendicular to the axial direction of the plunger and communicates with the group at the initial stage of injection after the plunger pressurizes the fuel in the high pressure chamber, and a communication hole is interposed in the fuel relief passage to meet operating conditions. By providing a variable cross-section orifice that changes the passage cross-sectional area according to the operating conditions, a part of the high-pressure fuel in the high-pressure chamber can be released to the pump chamber according to the operating conditions, and the initial injection rate can be reduced, especially for direct injection type. An object of the present invention is to provide an injection rate control device for a fuel injection pump that reduces NOx and noise by reducing the initial heat release rate in a diesel engine.

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

FIG. 2 shows a sectional view of essential parts of an embodiment of the present invention.

In the figure, a glue 2 (groove) 40 that is located between the suction port 12 and the distribution port 13 and surrounds the planter 7 is formed in the pump housing 31, and this group 40 and
A fuel relief passage 42 communicating with the pump chamber 5 to which fuel is supplied from the feed pump 3 is also bored in the pump housing 31 (actually, the group 40 and a part of the fuel relief passage 42 are formed in the pump housing 31). (formed in the axial direction 36).

On the other hand, from the center hole 37 drilled along the axial center of the plantar 7, a communication hole 41 that communicates with the group 40 for a predetermined section in the middle of the outgoing path of the plantar 7 (rightward in the figure) is connected to the center of the plantar 7 axis. Provided at right angles to the

Specifically, when the face cam 9 of the cam disc 8 is not on the roller 11, the communication hole 41 is on the left side of the group 40 and does not communicate with the face cam 9.
The plant gear 7 moves to the right and starts jetting by riding up on the roller 11, but at the beginning of the jetting, the communicating hole 41 communicates with the glue f40, and then from the middle of the jetting, the communicating hole 41 communicates with the glue f40.
crosses group 40, and now group 41 is also on the right side so that it does not communicate with it.

When the communication hole 41 and the group 40 are in communication, a part of the high pressure fuel in the high pressure chamber 6A pressurized by the movement of the planter 7 to the right is transferred to the communication hole 41, the group 40,
The fuel is returned to the pump chamber 5 via a fuel relief passage 42.

A variable cross section orifice 43 is provided in the fuel relief passage 42.
Interpose. The variable cross section orifice 43 may be located anywhere along the fuel relief passage 42, and in this embodiment, the main body 43A of the variable cross section orifice 43 is fixed to the pump housing song 31 by a threaded portion 43B.

FIG. 6 is an enlarged sectional view of this variable cross-section orifice 43.
In the valve chamber 43C, a valve body 43K is biased by a spring 43D in the axial direction of the main body 43A (rightward in the figure).
The seat surface 43H of E is pressed against the seat surface 43I of the main body 43A, and a passage 43G communicating between the fuel relief passage 42 and the pump chamber 5 is formed in the valve body 43E, and a small-diameter restrictor 43F is formed in this passage 43G. ing.

The fuel pressure that escapes to the fuel relief passage 42 when the communication hole 41 and the group 40 communicate differs depending on the operating conditions (the fuel pressure is higher in the high speed and high load range than in the low speed and low load range).
Therefore, when the fuel pressure in the low speed and low load range is low, the valve body 43E
In addition to the force due to the fuel pressure applied to the pressure receiving surface S (Figure 7 is a view from arrow P in Figure 6, the shaded area in the figure is the pressure receiving surface S), the initial load due to the spring 43D (the initial load is the shim 43J). (adjusted by the thickness of the valve body 43A) is larger so that the valve body 43E is pressed against the main body 43A, and when the fuel pressure is high in the high speed and high load range, the pressure is applied to the pressure receiving surface S of the valve body 43E. The spring constant, initial load, and area of the pressure receiving surface S of the spring 43D are selected so that the force overcomes the initial load of the spring 43D and increases the opening degree of the valve body 43E.

Therefore, in the low speed and low load range, fuel escapes through the passage 43G, and the amount of fuel that escapes at this time is defined by the diameter (cross-sectional area) of the throttle p 43F. In the high-speed, high-load range, the seat surface 43H of the valve body 43E and the seat surface 43I of the main body 43A change depending on the fuel pressure.
In addition to increasing the opening degree of the valve body 43 and passing through the passage 43G,
Fuel is also released from around F to increase the amount of fuel released.

Therefore, the variable cross-section orifice 43 is configured to change the cross-sectional area of the passage depending on the fuel pressure in the fuel relief passage 42.

Intake slits 38 are formed on the circumference of the planter 7 in the same number as the cylinders, and communicate the pump chamber 5 and the high pressure chamber 6A when the plantar member 7 rotates to the left during the suction stroke;
is formed by branching from the center hole, and communicates with the high pressure chamber 6 when the plant gear 7 rotates to the right during injection.
i. When the plant gear 7 rotates to the left after injection, the distribution boat 1
This is a pressure equalizing slit that communicates between the distribution boat 13 and the pump chamber 5 and releases the residual pressure (high pressure) in the passage between the distribution boat 13 and the delivery pump 14. The other components are the same as those in FIG. 1, so the same components are given the same reference numerals and their explanations will be omitted.

The effect of the above configuration will be explained based on the effect explanatory diagrams in FIGS. 3(5) to 3(5)).

As the seventh eighth cam 9 of the cam disc 8 descends from the roller 11, the planter 7 moves to the left while rotating, and when the intake boat 12 and the intake slit 38 of the planter 7 communicate with each other, the fuel in the pump chamber 5 is brought to a high pressure. Moving on to the suction stroke in which fuel is drawn into the chamber 6A, each passage such as the center hole 37, which communicates with the high pressure chamber 6A and is bored in the Flynn Soyer 7, is filled with fuel. Since the hole 41 is located on the left side of the group 4o, the fuel supplied to the high pressure chamber 6A does not escape to the pump chamber 5 (FIG. 3 (5)).

When the face cam 9 rotates and lifts up from one roller 11 to the next roller 11, the planter 7 also rotates and moves to the right, and the rotation of the planter 7 moves the suction boat 1
2 and the intake slit 38 are out of phase, and the intake boat 12 is closed. Therefore, the planter 7 pressurizes the fuel in the high pressure chamber 6A, and then the distributor slit 39
The pressurized high-pressure fuel pushes up the spring of the delivery valve 14 (FIG. 2), and an injection stroke begins in which the fuel is injected into the combustion chamber of the engine through the nozzle. At this time, the communication hole 41 approaches the group 40 (FIG. 3(B)).

When the communication hole 41 communicates with the group 40 at the beginning of injection in the injection stroke, a part of the high pressure fuel in the high pressure chamber 6A flows into the fuel relief passage 4.
Since fuel escapes to the pump chamber 5 through the variable cross-section orifice 43 (Fig. 2), the fuel flow rate (i.e., injection rate) supplied from the distribution boat 13 does not increase any further and reaches a plateau (Fig. 3 (Fig. 3)). C)).

In the middle of injection, the communication hole 41 comes to the right side of the group 40 and communication is cut off, and the fuel pressure in the high pressure chamber 6A starts to rise again, so the fuel flow rate sent out from the first distribution port 13 increases again from the peaked state ( Figure 3 (D)).

In the later stages of injection, the cutoff boat 15 comes off the right end surface of the control sleeve 16, so the high pressure fuel in the high pressure chamber 6A flows out from the cutoff boat 15 to the pump chamber 5, the fuel pressure in the high pressure chamber 6A decreases, and the fuel is pumped. ends (Fig. 3 (F21)).

When the fuel is pumped, the plunger 7 rotates and moves to the left (the face cam 9 descends from the roller 11), but on the way, the pressure equalizing slit 44 and the distribution boat 1 are removed.
3 communicate with each other, and the pressure (residual pressure) in the passage up to the delivery valve 14 (FIG. 2) is made equal to the hydraulic pressure in the pump chamber 5.

On the other hand, as the plunger 7 moves to the left, the communication hole 41 crosses the group 40, and then the suction port 12 and the next intake slit 38 communicate with each other, and the fuel in the pump chamber 5 is transferred to the high pressure chamber 6A.
The process returns to the suction stroke (FIG. 3(A)) in which the patient inhales, and the above-described operation is repeated.

However, the number of intake slits 38 on the circumference of the plunger 7 is the same as the number of cylinders, and the number of distribution boats 13 is the same as the number of cylinders on the circumference of the plunger 7.
Since there are the same number of cylinders around the cylinder, if the plunger 38 makes one reciprocation and fuel is sucked into the high pressure chamber 6A from the first intake slit 38, and the fuel is fed under pressure from the first distribution boat 13, the next plunger In one reciprocation of 38, fuel is taken in from the second intake slit 38, and fuel is pumped out from the second distribution boat 13, and it is not until the plunger 7 makes a reciprocating motion the same number as the number of cylinders that it reaches all cylinders. fuel supply will end.

Therefore, the fuel injection rate characteristic is K9 as shown by the solid line in Figure 4.
, compared to the injection rate characteristics of the conventional device (dashed line in Figure 4),
The injection rate at the beginning of injection is kept low. At this time, the heat release rate is as shown by the solid line in Figure 5, which is a smooth curve that does not have a sharp peak at the beginning of injection compared to the heat release rate with the conventional device (broken line in Figure 5). .

By the way, if only a portion of the amount of fuel is released from the high pressure chamber 6A through the fuel release passage 42, it is difficult to achieve the injection rate characteristics as shown by the solid line in FIG. 4 in all operating ranges.

For example, in a high-speed, high-load range, the injection rate increases as the plant speed increases, so unless the amount of fuel released through the entire fuel relief passage 42 also increases, the injection rate at the initial stage of injection cannot be kept low, and at low speeds Since the injection rate is low at low loads, the fuel escape amount matched to the high speed and high load range becomes too large, making it impossible to obtain the required injection rate and resulting in insufficient engine output.

For this reason, it is necessary to change the amount of fuel released through the fuel relief passage 42 depending on the operating conditions, and this amount of release is controlled by changing the cross-sectional area of the passage with the variable cross-section orifice 43.

This variable cross-section orifice 43 will be explained based on the operation explanatory diagram of FIG. Since the initial load due to the spring 43D is greater than the force due to the fuel pressure applied to the valve body 4 (shaded area in the figure),
Push the seat surface 43H of 3E onto the seat surface 43I of the main body 43A.
The fuel released from the high pressure chamber 6A is routed through the passage 43G.
The amount of fuel that escapes is determined by the cross-sectional area of the throttle D43F (FIG. 6 (5)).

In the high speed and high load range, the fuel pressure in the high pressure chamber 6A increases and the valve body 4
The force due to the fuel pressure applied to the pressure receiving surface S of the spring 43
Since the initial load of D is also larger, the spring 43D
The opening degree of the valve body 43E is increased to resist this, and the cross-sectional area of the passage between the seat surface 43H of the valve body 43E and the seat surface 43I of the main body 43A is increased.
(Fig. 6)
B)).

Therefore, since the variable cross-section orifice 43 controls the passage cross-sectional area according to the fuel pressure, the amount of fuel released is controlled according to the operating condition, and the injection rate characteristics are as shown by the solid line in Fig. 4 in all operating ranges. This is what happens.

FIG. 8 shows another embodiment in which the passage 43G penetrating the valve body 43K in FIG. 6 is shaped like a bag, whereas the passage 43K is formed in a simple straight shape.

The amount of fuel released is determined by the spring constant of spring 43D and shim 43.
It is determined by the combination of the initial setting load of the spring 43D determined by the thickness of the spring 43D and the area of the pressure receiving surface S of the valve body 43E, but if almost no pressure receiving area is required, this valve body 43E with the passage 43K in a straight shape may be used. Just use it.

As described above, a group that communicates with the pump chamber is formed around the planotsuya between the suction boat and the distribution boat, and a communication hole is formed from the center hole of the planotsuya at right angles to the axial direction of the planotsuya, and a group is formed at the beginning of injection on the outgoing path of the planotsuya. In addition, a variable cross-section orifice is installed in the fuel relief passage that communicates between the group and the pump chamber to change the passage cross-sectional area according to the fuel pressure, allowing the initial injection rate to be controlled under all operating conditions. As a result, heat generation at the initial stage of combustion is smoother, especially in direct injection diesel engines, and N
The effect is that Ox and noise levels are reduced.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the conventional device, Fig. 2 is a sectional view of the main part of the present invention, Fig. 3 is an explanatory diagram of the operation, Fig. 4 is an injection rate characteristic diagram, and Fig. 5 is a heat generation rate. The characteristic diagram, Figure 6, is an enlarged sectional view of the variable cross-section orifice.
B) is an explanatory view of the operation showing the high speed and high load region, FIG. 7 is a view taken along arrow P in the sixth position, and FIG. 8 is a sectional view of another embodiment of the valve body of the variable cross-section orifice. 5...Pump room, 6A...High pressure chamber, 7...Plantsya, 12...Suction boat, 13...Distribution boat,
37... Center hole, 40... Group, 41...
Communication hole, 42...Fuel relief passage, 43...Variable cross-section orifice. Patent Applicant Nissan Motor Co., Ltd. Figure 2・-403- Figure 3 (A) Figure 6 (D) Figure 3 (E) S1 Figure 4 Figure 5 Calibration Kufunfu PJ (degrees)

Claims (1)

[Claims] In a fuel injection pump for a diesel engine, a single blunt shaft rotates and reciprocates to suck fuel from a pump chamber into a high pressure chamber from a suction boat and distribute it to each cylinder from a distribution boat through a center hole. a group that is located around the blunt horn between the distribution boats and communicates with the pump chamber via a fuel relief passage; An injection rate control device for a fuel injection pump, characterized in that a communication hole that communicates with the group at the initial stage of injection and a variable cross-section orifice that is interposed in the fuel relief passage and changes the cross-sectional area of the passage according to operating conditions are provided. .