JPS61232332A - Fuel injection pump for internal-combustion engine - Google Patents

Abstract

PURPOSE:To suppress noise and Diesel knock, etc. by fitting a subplunger into a subchamber which communicates to a pumping chamber and controlling a fuel injection quantity adjusting member and a fuel injection timing adjusting member, interlocked with the operation of the subplunger. CONSTITUTION:A fuel injection pump discharges the fuel inhaled into a pumping chamber 12 by the movement of a plunger 3 which can be revolved and moved in reciprocation in the axial direction into a fuel injection nozzle from a discharge passage 16. In this case, a subchamber 21 communicating to the pumping chamber 12 is formed, and a subplunger 22 urged leftward by a spring 29 is fitted inside the subchamber 21. Said subplunger 22 is operated by a hydraulic actuator 27, which is drive-controlled by switching an electromagnetic selector valve 31 in a control circuit 33 according to the engine operation state. Further, interlocked with the switching of the electromagnetic selector valve 31, the hydraulic actuators 36 and 45 for controlling the fuel injection quantity and for controlling injection timing are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to improvements in fuel injection pumps for internal combustion engines, and particularly to improvements in fuel injection characteristics.

<Prior Art> As a distribution type fuel injection pump used in a small diesel engine, there is a conventional one as shown in FIG.

In the figure, a pump/distribution plunger 3 is slidably inserted into a plunger barrel 2 attached to a pump housing 1, and the plunger 3 is engaged with a cam disk 4 integrally formed at its base end. Matching camp ring 5
The drive shaft 6 rotates around the axis via the drive shaft 6. The cam disk 4 has the same number of face cams 4a as the number of cylinders of the engine, and the arc-shaped cam surface of the face cam 4a is mounted on a roller (cam follower member) 8 disposed in a roller holder 7 by a plunger spring 9. It rotates while being pressed and reciprocates by a predetermined cam lift.

Therefore, the plunger 3 reciprocates while rotating.

When the plunger 3 is in the suction stroke moving to the left in the figure, the fuel filling the inner space of the pump housing 1 is transferred from the suction boat 10 formed in the housing 1 and the plunger barrel 2 to the outer peripheral surface of the plunger 3. The liquid is sucked into a pumping chamber 12 formed between the end surface of the plunger 3 and the insertion hole 2a of the plunger barrel 2 through the suction groove 11 formed by the plunger.

Next, when the plunger 3 moves to the right in the drawing, the fuel in the pumping chamber 12 is pressurized and communicates with the through hole 13 formed in the plunger 3, which is opened on the outer peripheral surface of the plunger. From the distribution groove 14 to the insertion hole 2a
A discharge boat 15 opened on the inner peripheral surface and a discharge passage 16 formed in the housing 1. The fuel is injected and supplied into each cylinder from a fuel injection nozzle (not shown) via a delivery valve 17. Here, the discharge boats 15 are formed in the circumferential direction at equal intervals equal to the number of cylinders, and the reciprocating and
Oil is fed in a predetermined order along with the rotational movement.

A control sleeve 18 is slidably inserted into a portion of the plunger 3 that protrudes outside the insertion hole 2a, and a cut-off boat 19 that communicates with the through hole 13 and is opened on the outer peripheral surface of the plunger 3 is inserted into the control sleeve. 18, the fuel in the pumping chamber 12 flows out from the cant-off boat 19 into the low-pressure interior space of the housing 1, forming an injection path. Therefore, the injection end timing, that is, the injection amount can be controlled by adjusting the position of the control sleeve 18, and the position of the control sleeve 18 is determined by a governor mechanism and a control lever 20 that is linked to an accelerator pedal (not shown). Sankaido Published in March 1980 “Automotive Engineering Complete Book 5”
(Refer to pages 190 to 196 of “Diesel Engine”)
.

<Problems to be Solved by the Invention> However, with such conventional fuel injection pumps, there is a problem in the high speed range of the engine. In addition, the plunger diameter and cam profile of the cam disc are adopted to ensure fuel efficiency in the high load range, and the fuel injection rate in the entire operating range is determined at the same rate accordingly. Therefore, if the injection rate is too high in the low engine speed range, explosive combustion may occur, causing engine noise and diesel knock, and an increase in the injection rate in the low/medium load range may increase HC and NOx emissions. This was causing negative effects such as

The present invention has been made by focusing on these conventional problems, and provides a fuel injection pump for an internal combustion engine that solves the above problems by being able to switch to a favorable fuel injection rate depending on the engine operating condition. It is about providing.

Means for Solving Problems> Therefore, the present invention provides a sub-chamber formed in communication with the pumping chamber, a sub-plunger that is slidably inserted into the sub-chamber by a predetermined amount, and the sub-plunger. means for forcibly stopping the movement of the sub-plunger in a predetermined engine operating state; and a biasing force of the spring of the sub-plunger. a fuel injection amount adjusting means for adjusting the fuel injection amount by moving the fuel injection amount control member according to switching between when the movement is allowed against the movement and when the movement is stopped by the movement stopping means, and also a movement of the sub-plunger. The fuel injection timing adjusting means is provided for adjusting the fuel injection timing by moving the fuel injection timing control member according to the switching between the permission period and the movement stop period.

With this configuration, when the engine is running at low speed, the auxiliary plunger is allowed to move, and a predetermined amount of fuel discharged from the pumping chamber is sucked into the auxiliary chamber and then supplied to the fuel injection valve. For this reason, fuel is supplied at the portion where the moving speed due to cam engagement of the plunger is slow.
The fuel injection rate is reduced and noise, knocking, NOx, etc. can be improved.

On the other hand, at high speeds or high loads, by stopping the movement of the sub-plunger, fuel is supplied to the part where the movement speed is high due to cam engagement of the plunger, as in the past, so the fuel injection rate is increased and output is increased. can be ensured.

In addition, since the fuel injection amount and injection timing are adjusted according to the switching between the operating range that allows the sub-plunger to move and the operating range that stops the sub-plunger, fluctuations at the time of switching are suppressed and stable operation is achieved. Driveability can be ensured.

<Example> Embodiments of the present invention will be described below with reference to the drawings.

However, in the drawings of the embodiment, the same components as in the drawings of the conventional example are given the same reference numerals and explained.

In FIG. 1 showing the first embodiment, a bombing chamber 12
A sub-chamber 21 is formed which communicates with the plunger barrel 2 through a hole 2a formed in the top wall of the plunger barrel 2, and a sub-plunger 22 is fitted into the sub-chamber 21 so as to be freely slidable in the axial direction. The sub-plunger 22 has two stoppers 2 provided on both sides thereof.
The amount of movement is regulated by 3.24.

A small spring 46 is interposed between the left end surface of the sub-plunger 22 in the figure and the top wall of the plunger barrel 2, and biases the sub-plunger 22 to the right in the figure with a weak force.

In addition, a vacant room 2 is formed on the right side in the figure and is connected to the subchamber 21.
5 includes a spring washer 26 connected to the sub-plunger 22, a spring washer 28 connected to an output rod 27a of a first hydraulic actuator 27, which will be described later, and a spring washer 26, which is interposed between these two spring washers 26 and 28. A spring 29 is housed therein.

Here, the spring washer 28 can be moved by a larger amount of movement in the axial direction than the sub-plunger 22 due to the stroke of the output iron 27a. Further, when the output iron 27a is in the retracted position and the spring washer 28 is at the right end position in the figure, the spring 29 is in a free state between it and the spring washer 26 on the left side, and the sub plunger 22 is moved by the biasing force of the small spring 46. It is in the position where it is locked to the stopper 24.

The first hydraulic actuator 27 has a case 27b partitioned into two chambers by a piston 27C, and a chamber 27d on the left side in the figure is connected to an output port P of an electromagnetic switching valve 31 via a hydraulic line 30. The right chamber 27e is the hydraulic line 3
2 to the output port P2 of the electromagnetic switching valve 31.

The electromagnetic switching valve 31 includes an input port S+ connected to a low-pressure hydraulic source and an input port St connected to a high-pressure hydraulic source such as a hydraulic pump.
The connection between S2 and the two output ports Pl+P2 is switched by a spool valve body 31b that moves by turning on and off a solenoid 31a.

Specifically, the output signal from the control circuit 33, which is activated by inputting signals such as engine speed, fuel injection pump control lever opening (load), and start switch, activates the solenoid at low engine speeds and low load ranges. 31a is turned on and the spool valve body 31b is in the position shown in the figure, and the output port P1
is connected to the input port Sl on the low pressure side, and the output port Pz is connected to the input port sz on the high pressure side.

In addition, in other high speed ranges or high load ranges of the engine,
The solenoid 31a is turned ON, the spool valve body 31b is lowered in the figure, and the output port Pl is connected to the input boat St on the high pressure side.
, the output boat Pz is switched to be connected to the input port Sl on the low pressure side.

On the other hand, an adjustment pin 35 for adjusting the maximum fuel injection amount by coming into contact with one end of the collector lever 34 constituting the governor mechanism is attached to freely slide through the wall of the pump housing 1.
A second hydraulic actuator 36 is attached to the end of the adjustment pin 35.
output lots 36a are connected.

A chamber 36c on the left side in the figure defined by the piston 36b of the second hydraulic actuator 36 is connected to the hydraulic line 30.
The right chamber 36d is connected to the output port Pt of the electromagnetic switching valve 31 via the hydraulic line 32.

Then, the output rond 3 of the second hydraulic actuator 36
6a begins to extend, the adjustment pin 35 moves to the left in the figure, and as a result, the collector lever 34 moves to the fixed support shaft 37 in the figure.
The control sleeve 18 as a fuel injection amount control member is rotated by a predetermined angle counterclockwise around the collector lever 34, and the control sleeve 18 as a fuel injection amount control member is rotated to the right in the figure, that is, in the direction of increasing the fuel injection amount. It is supposed to move to .

Further, a timer piston 39 as a fuel injection timing control member is integrally incorporated in the fuel injection pump, and a chamber 40 on the left side of the timer piston 39 in the figure has a hydraulic pressure proportional to the engine rotation speed in the space inside the housing 1. was introduced,
The chamber 41 on the right side of the figure is connected to a low oil pressure source.

When the hydraulic pressure introduced from the chamber 40 increases in accordance with an increase in the engine rotational speed, the timer piston 39 moves to the right in the figure against the spring 42 that urges it leftward in the figure. The roller holder 7 is configured to rotate around a central axis (same axis as the plunger 3) via a rond (support shaft of the roller) 43 that engages with the roller.

As a result, the phase of engagement of the face cam 4a with the roller 8 is advanced, and the fuel discharge timing, that is, the fuel injection timing is advanced. The output rod 45a of the third hydraulic actuator 45 is connected to a spring washer 44 whose one end is locked to the spring 42.

A chamber 45c defined on the left side in the figure by the piston 45b of the third hydraulic actuator 45 is connected to the output port Pt of the electromagnetic switching valve 31 via the hydraulic line 32, and a chamber 45d defined on the right side is connected to the hydraulic out via line 30)
Connected to P+.

Next, the operation of this embodiment will be explained.

At low speed and low load (excluding when starting), the control circuit 33 is ON.
, the spool valve body 31b is in the illustrated position, and the output port Pl and the input boat S+-output port Pt and the input boat s2 are connected, respectively, so that the output terminal 27a of the first hydraulic actuator 27 is is at the left end position in the figure, and the output lot 36a of the second hydraulic actuator 36 is also at the left end position, but the output lot 44a of the third hydraulic actuator 45 is at the right end position in the figure.

In this state, the spring 29 is compressed and urges the sub-plunger 22 to the left in the figure. Here, the biasing force of the spring 29 is larger than the biasing force of the small spring 46, but is set to be sufficiently smaller than the opening pressure of a fuel injection nozzle (not shown) connected to the discharge bow 15.

Therefore, when the plunger 3 moves to the right in the drawing during the discharge stroke and the fuel pressure in the pumping chamber 12 increases, the sub-plunger 22 receives the fuel pressure and moves to the right in the drawing against the biasing force of the spring 29, and the stopper 3 moves to the right in the drawing. 24 and stop.

During this time, the fuel in the stroke volume of the sub-plunger 22 is transferred to the sub-chamber 2.
It is sucked out within 1. That is, a portion of the fuel discharged from the plunger 3 is used to move the sub-plunger 22, and the increase in fuel pressure is delayed accordingly.

As a result, as shown in FIG. 2a, the movement speed (
Since fuel injection is performed in a portion where the crank angular velocity is small, an injection rate waveform with a low injection rate and a long injection period can be obtained.

FIG. 2b shows the portion where the cam lift is used during the conventional injection period under the same conditions.

However, this alone will delay the start of fuel injection, but at the same time as the electromagnetic switching valve 31 is switched to the illustrated position, high-pressure oil is introduced into the chamber 45c of the third hydraulic actuator 45, and the chamber 45d becomes a low-pressure oil source. In communication, the spring washer 44
moves to the right in the figure, the timer piston 39 moves to the right by a predetermined amount and moves the roller holder 7 to the fuel injection timing advance side by the amount of delay in fuel injection timing due to the movement of the sub-plunger 22. Delays in the start of injection can be prevented.

Note that the fuel injection timing may be configured to be different depending on the difference in operating conditions between the low speed/low load range and the other high speed/high load range.

Further, the second hydraulic actuator 36 has a chamber 36d.
High-pressure oil is introduced into the chamber 36c, and the chamber 36c communicates with the low-pressure oil source, so the output iron 36a extends to the left in the figure and is controlled by moving the adjustment bin 35 and rotating the collector lever 34 and tension lever 38. The sleeve 18 moves in the direction of increasing the fuel injection amount.

That is, as mentioned above, since the fuel injection rate was reduced,
Therefore, it is necessary to lengthen the injection period to secure the fuel injection amount, and after a certain amount of time has passed after switching the solenoid switching valve 31, the governor mechanism will automatically control the control, but immediately after switching, the response will be delayed. Since the fuel injection amount will temporarily decrease, in order to prevent this, the increase in the fuel injection amount is adjusted at the same time as switching.

In this way, since the fuel injection amount and fuel injection timing can be adjusted at the time of switching, torque fluctuations, etc. at the time of switching can be avoided, and stable drivability can be maintained.

In the engine's high speed range above the specified level or the high load range above the specified level,
The energization from the control circuit 33 to the electromagnetic switching valve 31 is turned off, the spool valve body 31b is set to the lowered position in the figure, and the output port P+ is connected to the input boat Sz, and the output port Pt is connected to the input port S, respectively. Switched connection is made. As a result, the first hydraulic actuator 27 operates in the chambers 27d and 27.
By switching the oil pressure to e, the output rod 27a is retracted and the spring washer 28 moves to the right in the figure, and the bias of the spring 29 to the sub-plunger 22 is released and the sub-plunger 22 is in the position where it is locked to the stopper 24. Stop.

Therefore, the introduction of fuel from the pumping chamber 12 to the auxiliary chamber 21 is stopped, and all the discharged fuel is sent under pressure to the fuel injection valve through the discharge port 15, and as in the past, a high injection rate characteristic that is well suited to the relevant operating range can be obtained. It will be done.

On the other hand, in the second hydraulic actuator 36, the output rod 36a is similarly retracted by switching the hydraulic pressure, and the control sleeve 18 is moved by a predetermined amount in the direction of decreasing the fuel injection amount.
As the output rod 45a of the third hydraulic actuator 45 also extends, the timer piston 39 moves by a predetermined amount in the direction of retarding the fuel injection timing via the spring washer 44.

That is, the control sleeve 18. timer piston 3
9 are both returned to positions corresponding to the conventional fuel injection rate characteristics.

As a result, fuel injection characteristics suitable for high speed or high load ranges can be obtained as in the conventional case, and good drivability can be ensured.

3 to 6 show different embodiments of switching means for permitting movement and stopping movement of the sub-plunger, respectively.

The switching valve 51 shown in FIG. 3 is formed with a hole 51a passing through the diametrical direction of a cylindrical member, and is connected to an actuator (not shown) to rotate around an axis, and in the shown position, the passage 52 is closed. Since the introduction of discharged fuel from the pumping chamber 12 to the auxiliary chamber 21 is blocked, movement of the auxiliary plunger 22 is stopped, and movement of the auxiliary plunger 22 is allowed at the position where the hole 51a overlaps the passage 52.

The switching valve 61 shown in FIG. 4 is moved in the axial direction by a solenoid 61a so that a circumferential groove 61b formed in the center overlaps or blocks the passage 52.

The one shown in FIG. 5 is a switching valve 7 that uses a solenoid 71c to open and close a pawl valve body 71b that is biased by a spring 71a.
1, and has excellent sealing performance when the valve is closed.

What is shown in FIG. 6 is the pumping chamber 12. A three-way switching valve 81 is provided in a passage 80 formed by connecting a passage 52 connecting the auxiliary chambers 21 and a cavity 25 communicating with the back surface of the auxiliary plunger 22.

In the position of the switching valve 81 shown in FIG. 6, the passage 80 is closed to allow movement of the sub-plunger 22, and in the position shown in FIG. The movement of the sub plunger 22 is stopped by applying the same back pressure as . In the position shown in FIG. 6(2), the empty chamber 25 is communicated with the fuel tank (low pressure source) 82 so that the fuel accumulated in the empty chamber 25 is returned to the fuel tank 82.

(Effects of the Invention) As explained above, according to the present invention, by allowing the sub-plunger to move in low-speed, low-load ranges, etc., fuel can be injected in areas where the moving speed due to cam engagement of the plunger is small. As a result, the fuel injection rate can be reduced to avoid explosive combustion, noise and diesel knock can be prevented, and emissions of HC, NOx, etc. can also be reduced.

Further, since the fuel injection amount and the injection timing are adjusted according to the switching between when the movement of the sub-plunger is allowed and when the sub-plunger is stopped, a shock at the time of switching can be avoided and stable drivability can be maintained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the overall configuration of the first embodiment of the present invention, Fig. 2 is a diagram showing the lift portion of the plunger corresponding to the fuel injection timing at low speed and low load, and Figs. 6th
The figures are sectional views of the main parts of the second to fifth embodiments of the present invention, in which Figure 6 shows the state when the sub plunger is allowed to move, and Figure 6 shows the state when the movement is stopped. FIG. 7 is a sectional view showing an example of a conventional general distribution type fuel injection pump. 2...Plunger barrel 3...Plunger 4a
...Face cam 8...Roller 12...
Bumping chamber 18...Control sleeve 21
... subchamber 22... subplunger 23.24
... Stopper 27 ... First hydraulic actuator
29...Spring 30.32...Hydraulic line 31...Solenoid switching valve 33...Control circuit 3
5...Adjustment bin 36...Second hydraulic actuator 39...Timer piston 45...Third hydraulic actuator Patent applicant Nissan Motor Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A pumping chamber is formed between the plunger barrel and the plunger by reciprocating the plunger inserted into the plunger barrel in the axial direction through engagement between the cam surface formed at its base end and the cam follower member. a fuel injection amount control member that controls the amount of fuel injected by controlling the amount of fuel injected into the fuel injection nozzle, and a phase of engagement between the cam surface and the cam follower member. In the fuel injection pump for an internal combustion engine, the fuel injection pump includes a fuel injection timing control member that controls the fuel injection timing by a fuel injection timing control member, and a subchamber that is formed in communication with the pumping chamber, and a fuel injection timing control member that is slidably inserted by a predetermined amount into the subchamber. a sub-plunger,
a spring that urges the sub-plunger in a direction to reduce the volume of the sub-chamber space communicating with the pumping chamber; a means for forcibly stopping the movement of the sub-plunger in a predetermined engine operating state; and the spring of the sub-plunger. a fuel injection amount adjusting means for adjusting the fuel injection amount by moving the fuel injection amount control member according to switching between when the movement is allowed against the urging force of the movement stopping means and when the movement is stopped by the movement stopping means; Fuel injection for an internal combustion engine, characterized in that it is provided with a fuel injection timing adjustment means for adjusting the fuel injection timing by moving the fuel injection timing control member according to switching between when the plunger is allowed to move and when the movement is stopped. pump.