JPS58190561A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To optionally control the maximum pressure of high pressure injection and improve operative performance, by forming an oil-tight chamber neighboring to a pressure chamber pressurized through a shuttle movable plunger and providing a control piston for regulating fuel pressure to said oil-tight chamber. CONSTITUTION:If a plunger 1 performs shuttle motion by a face cam rotated interlocking to an engine, sucked fuel into a pressure chamber 3 via a suction hole 2a, after being pressurized, is forcibly fed to an injection nozzle, not shown in the drawing, through a delivery groove 1b and delivery hole 2b. Here if pressure in the chamber 3 overcomes tension of a spring 12, fuel in the chamber 3 presses to open a check valve 13 and flows into an oil-tight chamber 30 to move a control piston 10 rightward, when the chamber 30 is communicated to a control hole 14, a part of fuel is returned to flow in a pump chamber 101. A maximum pressure in the above chamber 3 is regulated by rotating the piston 10 with a step motor 11 through gears 19, 18 and adjusting a relative position between a control face 10a of the piston 10 and the hole 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection pump, and in particular:
This paper relates to a control mechanism for the injection pressure, which has a large effect on the injection rate, spray particle size, distribution, and injection penetration force of the fuel injection pump of an internal combustion engine.

In conventional fuel injection pumps, the fuel pressure is determined by the crank angle, considering, for example, the same injection, since the movement of the fuel pumping plunger is determined by a cam synchronized with the engine. For this reason, if the rotation speed changes, the time will differ even at the same angle, so the injection amount per unit time (ml ejection rate)
As a result, the injection pressure changes as shown in FIG. 1, for example.

However, the optimum injection pressure or injection rate from the engine's perspective is not easily determined, and in addition to the number of volumes, there are
This varies greatly depending on various variables such as load, cooling water temperature, altitude, exhaust gas circulation amount, intake throttle, etc., but it is not possible with current injection devices to meet these demands. Therefore, there has been a strong desire to propose a practical device that can directly control injection pressure.

The present invention was made in consideration of the above needs,
The purpose of the present invention is to provide a fuel injection pump in which the maximum pressure of high-pressure injection can be arbitrarily controlled, that is, the relief pressure can be varied. (2) a check valve that allows fuel to flow only from the pressurized chamber toward the oil-tight chamber; a control piston having a control surface facing the oil-tight chamber; A spring biased in a pressurizing direction, and a control hole communicated with or shut off from the oil-tight chamber by the control surface, and by adjusting the relative position of the control surface and the control hole, the pressure inside the pressurization chamber can be adjusted. It is characterized by controlling the maximum pressure.

A first embodiment of a fuel injection pump for a diesel engine having an injection pressure control device of the present invention will be described with reference to FIGS. 2 to 5.

FIG. 2 is a diagram showing the injection pressure control device 100 provided in the housing 2 of the distribution type fuel injection pump. In FIG. 2, a plunger 1 is slidably inserted into a housing 2 and is rotated and reciprocated by a cam means (not shown). body 4
and housing 2 are fixed in an oil-tight manner with bolts 6, and bodies 5 and 4 are fixed in an oil-tight manner with bolts 9.

(3) Furthermore, the seat 8 is pressed into contact with the housing 2 and the body 4 in an oil-tight manner.

The control piston IO is slidably and rotatably fitted to the body 4 in an oil-tight manner. A groove is cut into the gear holder 22 and the control piston 10, which is sufficient for the steel ball 20 to enter.The gear holder 22 and the control piston 10 are relatively restricted in the rotational direction, but are prevented from sliding in the axial direction of the piston. They are movably fitted. The gear 18 is press-fitted into the gear holder 22, and the stopper pin 17 is press-fitted into the plate 15 and comes into contact with the convex part of the gear holder 22, so that the control piston 10
Used for rotational positioning.

The plate 15 has a protrusion 15a that serves as a stopper for the pressure plate 16, which is urged leftward in FIG. 2 by the spring 12.
The amount of protrusion is between this protrusion 15a and the pressure plate 1.
Spring 1 against control piston IO upon contact with 6
The dimensions are sufficient so that the load due to 2 is not applied.

A thrust bearing 21 (4) is provided at the right end of the suspension ring 12 in FIG. 2, and the body 5 and the spring 12 can rotate freely.

The check valve 13 is biased by a spring 7 in a certain direction of the plunger l.

Next, the operation will be explained. The plunger 1 performs rotational movement in synchronization with a diesel engine (not shown), and at the same time performs reciprocating movement in the left-right direction in FIG. During the stroke, the suction groove 1a cut at the tip of the plunger 1 and the suction hole 2a extending into the housing 2 communicate with each other, and the fuel in the pump chamber 101 is introduced into the pressurizing chamber 3. Further, when the plunger 1 is in the discharge stroke moving to the right in the figure, the discharge groove 1 communicates with the pressurizing chamber 3 through a hole (not shown) provided in the center of the plunger 1.
b communicates with a discharge hole 2b extending into the housing 2, and the fuel in the pressurized chamber 2 is introduced from the discharge hole 2b to a nozzle (not shown).

During the discharge stroke, the pressure inside the pressurizing chamber 3 increases and the spring 1
When the size is large enough to resist the load of 2, pressurize (5) Pressure chamber 3F! 3 flows into the oil-tight chamber 3o and moves the control piston 10 to the right. When the oil-tight chamber 3o and the control hole 14 communicate with each other, the control piston 1o stops, and some of the fuel in the pressurized chamber 3 is the oil-tight room 30. It passes through the control hole 14 and is returned to the pump chamber 101. In other words, the pressure inside the pressurizing chamber 3 is the same as that of the spring 12 when the oil-tight chamber 3o and the control hole 14 communicate with each other.
When the pressure is less than the pressure balanced with the load of the spring 12, the fuel in the pressurized chamber 3 is sent to the discharge hole 2b, but when the pressure tries to exceed the pressure balanced with the load of the spring 12, part of the fuel in the pressurized chamber 3 is controlled. Since it passes through the hole 14 and escapes into the pump chamber 101, the pressure increase in the pressurized chamber is suppressed.

Next, the pressure in the pressurized chamber 3 after the injection has finished has decreased (
In this case, the fuel in the oil-tight chamber 30 cannot return to the pressurizing chamber 3 due to the action of the check valve 13, so the control piston 10
The lead surface forming the control surface 10a provided in the control hole 14
At the position where the oil-tight chamber 30 is closed, the oil-tight chamber 30 is cut off from the outside and enters an oil-tight lock state.

Therefore, the control piston 10 cannot return to the initial position (6), and during the subsequent discharge stroke, the control piston 10 controls the pressure in the pressurizing chamber 3 without moving much. .

Next, by rotating the step motor 11, its rotational torque is amplified by the gears 19 and 18 and transmitted to the control piston 10 via the gear holder 22 and steel balls 20 press-fitted into the gears 18. Control piston 10 from the state shown in the figure
For example, when rotated by 180 degrees, since the control surface 10a, which is the tip surface of the control piston 10, is inclined as a lead surface, the relative distance in the axial direction between the control hole 14 and the control surface 10a changes, and the oil-tight chamber 30 through the control hole 14 to the pump chamber 1
01, the control piston 10 must be further moved to the right in the figure. When the pressure inside the pressurizing chamber 3 rises sufficiently during the first discharge stroke after the rotation of the control piston 10, the oil-tight chamber 30 and the pump chamber 101 continue to communicate with each other through the control hole 14. The control piston 10 moves to the right. The load applied by the spring 12 at this time is the control piston 10 (7
) becomes larger than the balanced state before rotating, and the pressure within the oil-tight chamber 30 to balance the load also becomes larger. When the pressure in the pressurizing chamber 3 attempts to exceed the pressure balanced with the load of the spring 12, the fuel in the oil-tight chamber 30 passes through the control hole 14 and flows out into the pump chamber 101, so that the pressure increase is suppressed.

By controlling the rotation of the control piston 10 in this way, the set load of the spring 12 when the control hole 14 is opened can be changed as shown in FIG. This means that the maximum pressure can be controlled.

The reason why the control piston 10 is prevented from returning by the check valve 13 is that in order to cause the control piston 10 to reciprocate for each injection stroke, fuel must be supplied to the oil-tight chamber 30 for each discharge stroke. The purpose of this invention is to prevent injection delays caused by a decrease in the oil delivery rate from the pressurizing chamber 3 to the discharge hole 2b, and irregular injections such as two-stage injection due to the mass effect of the control piston 10. It also prevents fatigue failure of the spring 12, the plane (8), the plate 16 of the control piston 10, and the plate 15 of the control piston 10.
There are various advantages such as prevention of shock damage caused by collision with the control piston 10 and prevention of wear of the grooves and the like on the outer circumference of the control piston 10 and the steel ball holder.

Further, a protrusion 15a corresponding to a contact portion between the thrust bearing 21 and the pressure plate 16 of the plate 15 is provided.
is for reducing the rotational torque of the control piston 10, and the size of 15a is the pressure play in the initial state)
16 and the protrusion 15a, the protrusion 15a receives all the load of the spring 12 and has a sufficiently long dimension so that the load of the spring 12 is not applied to the control piston 10. Therefore, when the step motor 11 is rotated in this state, the control piston 10 rotates, but the pressure plate 16 and the spring 12 do not rotate. Furthermore, when the pump is activated and the pressure plate 16 and the protrusion 15a are separated, the pressure plate 16 and the spring 12 rotate together with the control piston 10;
The thrust bearing 21 makes rotational resistance extremely small (9).

The stopper pin 17 is for positioning the control piston 100 rotations, and the origin of rotation is determined by contact with the protrusion of the gear holder 22.

FIG. 5 shows measurement waveforms of the needle lift amount and injection rate of the injection nozzle obtained when the maximum pressure Pw+ax in the pressurizing chamber 3 of the present invention is controlled, and shows the end of pressurization by the pump rotation speed and the accelerator lever. The timing etc. are fixed, and only the spring load when the control hole is opened is changed.

Inevitably, when controlling the maximum pressure, the injection amount decreases by the amount of leakage, but by using the accelerator lever (not shown) to delay the injection end time and increase the amount by the decrease, the injection amount remains constant and the injection time is increased. It can be extended. By extending the injection time, efficient combustion can be performed during low-speed operation, improving engine performance and reducing noise during idling.

A second embodiment is shown in FIG. To explain the difference from the first embodiment, this is a control piston 1 with the control surface 10a as the lead surface as in the first embodiment (10).
In this example, the control surface 10a is set as a surface perpendicular to the central axis of the control piston 10, and the control hole 14 is slidably controlled by hydraulic pressure, instead of controlling the rotation of the control surface 10a. By introducing pressure-controlled fluid into the pressure chamber 42, the control hole 14
The sleeve 42, which has a .

FIG. 7 shows a third embodiment in which the injection pressure control device 100 shown in FIG. Figure 7 shows 1
Although only the cylinder is shown, the rotation of the control pistons of other cylinders (not shown) is also controlled by the gear 50 at the same time.

FIG. 8 shows a fourth embodiment in which the rotation of a cylinder 60 having a control hole 14 is controlled without rotating the control piston 10.

FIG. 9 shows detailed shapes of the control piston 10, plate 15 and pressure plate 16 of FIG.

FIG. 10 is a front view and a side view of the tip of the control piston 10 showing another example of the shape of the lead surface forming the control surface 10a at the tip of the control piston 10. FIG. The embodiments shown in Figures 1 and 8 have slopes numbered as shown in Figure 10(a), but they may also have a spiral shape as shown in Figure 10(a). The birch-like axisymmetric shapes shown in (C) and (d) may also be used.

As explained in detail above, the present invention provides a fuel injection pump that pumps fuel by reciprocating the plunger l which is slidably fitted in an oil-tight manner to the housing 2, in which pressure is applied to the tip of the plunger. an oil-tight chamber 30 communicating with the chamber 3; a check valve 13 between the pressurizing chamber 3 and the oil-tight chamber 30 that allows fuel to flow only from the pressurizing chamber 3 toward the oil-tight chamber 30; and the oil-tight chamber 30. control piston 10 with control surface IQ'a facing
, a spring 12 that urges the control piston 10 in a direction to pressurize the fluid in the oil-tight chamber 30, and the control surface 1.
The control surface 10a and the control hole 1 are provided with a control hole 14 that communicates with or is in turn blocked from the oil-tight chamber 30 by 0a.
Since the maximum pressure in the pressurizing chamber 3 is controlled by adjusting the relative position with respect to the pressurizing chamber 3, it is possible to make the fuel injection pressure variable, and the movement of the control piston, which has a relatively large mass, is extremely small. Therefore, compared to the conventional Akinimulator type, it is possible to track the speed better even at high speeds, and it is possible to obtain a large control range under a wide variety of operating conditions.

[Brief explanation of the drawing]

FIG. 1 is a graph showing how the maximum injection pressure in a conventional fuel injection pump changes depending on the pump rotation speed. 2 to 5 relate to the first embodiment of the present invention, and FIG. 2 shows the injection pressure control device 1 which constitutes the main part of the present invention.
883 to 5 are characteristic diagrams of the fuel injection pump of the first embodiment. Fig. 6 is a side sectional view of the second embodiment, Fig. 7 is a side sectional view of the j83 embodiment, Fig. 1148 is a side sectional view of the fourth embodiment, and Fig. 9 is a partial side sectional view of the fourth embodiment. This is a detailed view, and the first
Figure 0 is a front view and a side view (13) of another example of the shape of the lead surface forming the control surface 10a. ■...Plunger, la...Suction groove, 1b...Discharge groove, 2...Housing, 2a...Suction hole, 2b...
...Discharge hole, 3...Pressure chamber, 4...Body, 5...
・Body, 6... Bolt, 7... Spring, 8.
... Seat, 9... Bolt, lO... Control piston, 10a... Control surface, 11... Step motor, 1
2... Spring, 13... Check valve, 14... Control hole, 15... Plate, 16... Pressure plate, 17... Stopper bin, 1B... Gear,
19... Gear, 20... Steel ball, 21... Thrust bearing, 22... Gear holder, 30... Oil-tight chamber, 40... Spring, 41... Pressure chamber, 42...
・Sleeve, 50...Rack gear, 60...Cylinder, 100...Injection pressure control device%' tot・
··pump room. Representative Patent Attorney Takashi Okabe (14) Figure 1 Figure 2 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9, Figure 10

Claims (1)

[Claims] In a fuel injection pump that pumps fuel by reciprocating a plunger that is slidably fitted in an oil-tight manner in a housing,
an oil-tight chamber communicating with the pressurizing chamber at the tip of the plunger; a check valve that allows fuel to flow only from the pressurizing chamber toward the oil-tight chamber between the pressurizing chamber and the oil-tight chamber; a control piston having a control surface; a spring that biases the control piston in a direction to pressurize fluid in the oil-tight chamber; and a control hole communicated with or blocked from the oil-tight chamber by the control surface; A fuel injection pump characterized in that a maximum pressure in the pressurizing chamber is controlled by adjusting a relative position between a control surface and the control hole.