JPH11280587A - Pressure accumulator type fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve small amount injection controllability without changing pressure receiving area on the upper and lower sides of a needle leading to fuel leakage, thickening of a diameter and an increase in cost. SOLUTION: Small amount injection controllability can be improved because a check valve 200 preventing back flow from a control chamber 13 to a restriction 12a of an entrance part to the control chamber 13 is provided without changing pressure receiving area on the upper and lower sides of a needle T. The check valve 200 is provided at the inside of a plate and the check valve 200 is a ball valve constituted of a tapered surface 12b seating a ball 20 and a ball 20. The lift amount of the check valve 200 is regulated and the check valve 200 is made to have a second restriction effect by the regulated lift. A week energizing mechanism such as a week spring is provided at the back of the check valve 200.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator type fuel injection device mainly used as a fuel injection device for a diesel engine.

[0002]

2. Description of the Related Art In order to improve the controllability of injection of a small amount of fuel and the responsiveness of valve closing of a needle, a pressure accumulating type fuel injection system has a pressure receiving area above and below the needle as disclosed in, for example, JP-A-7-29387. Alternatively, a method of increasing the pressure receiving area in the upper control chamber and decreasing the pressure receiving area in the lower needle chamber below the oil reservoir is often adopted.

However, if the pressure receiving area at the top and bottom of the needle is changed, a step is formed in the sliding portion in the body, which requires a gap at least for the operating distance of the needle near the step between the needle and the body. Therefore, fuel leaks from the control chamber or the needle chamber to the gap through the sliding portion. Fuel leakage causes power loss in the system. However, as the injection pressure increases, the leakage increases dramatically, so that the system loss also increases and the fuel efficiency under a high load is significantly deteriorated. In addition, a return flow path for discharging leaked fuel to the outside is required, which leads to an increase in body diameter and cost. For these reasons, it is necessary to improve the controllability of the small amount injection without changing the pressure receiving area above and below the needle.

The poor controllability at the time of small-volume injection is due to the slow response of the valve-closing start when the needle is lifted halfway. This is because during the midway lift (during needle rising), the pressure in the high-pressure fuel flow path that is located upstream of the control chamber and the throttle and communicates with the accumulator is almost equal, so that the fuel can flow backward from the control chamber to the upstream. Yes, this causes a further rise due to the inertia of the needle.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve controllability of small-volume injection without changing the pressure receiving area above and below the needle, which leads to fuel leakage, increase in diameter, and increase in cost. is there.

[0006]

In order to solve the above-mentioned problems, the present invention employs the technical means described in claims 1 to 5. According to the first aspect of the present invention, since the check valve for preventing the backflow to the high-pressure flow path side via the throttle at the entrance from the control chamber to the control chamber is provided, the small-quantity injection controllability can be improved. .

According to the second aspect of the present invention, since the check valve is provided inside the plate, it can be formed compact, and only the plate 12 forming the control chamber needs to be processed. According to the third aspect of the present invention, since the check valve is a ball valve having a ball and a tapered surface for seating the ball, the check valve can be formed with a simple configuration.

According to the fourth aspect of the present invention, the lift amount of the check valve is regulated, and the check valve is given the second throttle effect by the regulated lift. Is obtained. According to the invention described in claim 5,
Since a weak urging mechanism such as a weak spring is provided behind the check valve, a reliable valve closing operation can be obtained when the valve is closed.

[0009]

1 to 3 relate to a first embodiment of the present invention. FIG. 1 is a cross-sectional view taken along a central axis, showing the entire structure of a pressure accumulating fuel injection device to which the present invention is applied. 2, FIG. 2 is a partially enlarged cross-sectional view showing a main part around the check valve ball 20 in FIG. 1, and FIG. 3 shows the lift of the needle 7 at the time of a small injection command in both cases with and without the check valve. It is a characteristic view which shows a time change.

1 and 2, a body 1 is connected to a packing tip 2, a stopper 3, and a nozzle body 4 in this order, and is fastened together by a retainer 5. A piston rod 6 is slidably supported in the body 1, and is supported at the lower end by a gap in the axial direction with an upper end of a needle 7 which is also slidably supported in the nozzle body 1. The joint 8 is used for the connection.

The needle system consisting of the piston rod 6, the needle 7, and the joint 8 is urged downward by a spring 9, and the tapered surface 7a at the tip of the needle 7 is normally seated on the seat 4a at the tip of the nozzle body 4. For the needle system, except for the piston rod head 6b, for example, the sliding portion 6
A fuel passage is provided by three-chamfering such as a and 7b, and fuel can be supplied from the inlet 10 forming the high-pressure flow passage to the needle chamber 11 without restriction.

The fuel passes from the inlet 10 to the control chamber 13 in the plate 12 through an orifice IN12a which restricts the entrance to the control chamber 13.
And control room 13 surrounded by body 1 and plate 12
It is stored in. Further on the plate 14 is located,
An orifice OUT14a is provided inside the flow passage leading to the control chamber 13 and at the end thereof. The plate 12 and the plate 14 are fastened together with the body 1 at a valve body 15 on the upper side thereof.

The valve 16 which constitutes the hydraulic control valve comprises a valve plate 16a which is supported to be tiltable, a valve stem 16b which is slidably supported inside the valve body 15 and an armature 16c which receives the magnetic force of a solenoid 17.
A spring for biasing the valve 16 on the plate 14 is contained in the solenoid 17. Inlet 1
When the high-pressure fuel is introduced from zero, the needle system shows that the downward force caused by the pressure applied to the upper side of the piston rod head 6b, that is, the pressure applied to the control chamber 13, is compared with the force caused by the pressure applied to the lower side of the piston rod head 6b. Since it is larger by the area of the sack 4 b at the tip of the body 4, the seat 4 a is urged by the force difference and the force of the spring 9.

A feature of the present invention is that a check valve 200 for preventing backflow is provided downstream of the orifice IN12a in the plate 12 (on the control chamber 13 side). Check valve 20
Numeral 0 is composed of the ball 20 and the tapered surface 12b.
Next, the operation will be described. When the solenoid 17 is energized, the armature 16c receives a magnetic force and pulls up the entire valve 16. The valve plate 16a is the plate 14
Away from the orifice OUT14a, high-pressure fuel accumulated in the control chamber 13 is ejected from the orifice OUT14a, and the pressure in the control chamber 13 becomes equal to the orifice IN12a and the orifice OUT14a.
Descend according to the area of.

The downward force on the needle system is weakened by the pressure drop in the control chamber 13, and the needle system is lifted by the weakening of the needle system due to the hydraulic pressure below the head 6 b of the piston rod 6. The fuel is injected from the injection hole 21. When the energization of the solenoid 17 is cut off, the valve 16 is lowered by the spring force of the spring in the solenoid 17, the valve plate 16a is seated on the plate 14, and the outflow from the control chamber 13 to the downstream is stopped. Therefore, the needle system descends due to the inflow of fuel from the orifice IN12a, and eventually sits on the seat 4a,
The injection ends.

At the time of a small injection command, the solenoid 1
The valve 16 closes while the needle system is rising because the current supply to the valve 7 is accelerated. However, during opening the orifice I
Since there is almost no pressure difference before and after N12a, if there is no check valve 200, the rise due to the inertia of the needle system is allowed, and the fuel in the control chamber 13 flows back through the orifice IN12a. This is a cause of the fact that the actual valve closing is greatly delayed from the valve closing command in the accumulator type fuel injection device without the check valve 200.

FIG. 3 shows the lift of the valve 16 at the time of the small injection command in both cases where the check valve 200 is used or not.
The flow rate of the fuel flowing into the control chamber 13, the pressure of the control chamber 13, the lift of the needle 7, and the time change of the injection rate (the flow rate of the injection hole 21) are shown. As can be seen from this figure, when the check valve 200 is not provided, after the valve 16 is closed, the orifice IN12a
It is evident that the fuel flows backward, which makes it possible to raise the needle system by inertia after the valve 16 is closed. By providing the check valve 200, the needle system can be closed after the valve 16 is closed. It can be seen that it has started immediately.

From the above, it can be seen that the use of the present invention makes it possible to control the small amount injection without changing the pressure receiving area of the needle system up and down and without unnecessarily lowering the initial injection rate. FIG. 4 relates to a second embodiment of the present invention.
FIG. 2 is a partially enlarged cross-sectional view showing a main part around 0.

The second embodiment shown in FIG. 4 is an embodiment of the present invention in which the lift of the check valve 200 is restricted and the check valve 200 has a throttling effect. A ball stopper 22 is provided.
FIG. 5 relates to a third embodiment of the present invention, and is a partial cross-sectional view showing a main part around a ball 20 of a check valve 200.

FIG. 5 shows a third embodiment of the present invention in which a weak spring 23 is provided as a biasing mechanism behind the check valve 200, and the leaf spring 23 and the adjusting shim are provided. 24. In the embodiments shown in FIGS. 4 and 5, it may be necessary to set an orifice in consideration of the pressure loss.

[Brief description of the drawings]

FIG. 1 relates to a first embodiment of the present invention, and is a cross-sectional view along a central axis showing an overall configuration of a pressure accumulating fuel injection device to which the present invention is applied.

FIG. 2 relates to the first embodiment of the present invention, and is a partially enlarged cross-sectional view showing a main part around a ball 20 of the check valve in FIG.

FIG. 3 relates to the first embodiment of the present invention, and is a characteristic diagram showing a time change such as a lift of a needle 7 at the time of a small injection command in both cases with and without a check valve.

FIG. 4 relates to a second embodiment of the present invention and is a partially enlarged cross-sectional view showing a main part around a ball 20 of a check valve 200.

FIG. 5 relates to a third embodiment of the present invention, and is a partial cross-sectional view showing a main part around a ball 20 of a check valve 200.

[Explanation of symbols]

 Reference Signs List 6 piston rod 6b head of piston rod 7 needle 10 high-pressure flow path (inlet) 12a throttle at inlet to control room (orifice IN) 12 plate 12b tapered surface 13 control room 16 hydraulic control valve (valve) 20 ball 23 weak Energizing mechanism (spring) 200 Check valve

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 61/10 F02M 61/10 S

Claims (5)

[Claims] 1. A high pressure flow path communicating with a piston rod formed separately or integrally with a needle, a control chamber adjacent to a head of the piston rod, and a pressure accumulating vessel storing high pressure fuel. A pressure-accumulation type fuel injection device, comprising: a throttle at the entrance to the control chamber, and a hydraulic control valve, wherein the pressure in the control chamber is adjusted by controlling the hydraulic control valve to adjust the fuel injection time. A pressure-accumulating fuel injection device, further comprising a check valve for preventing a backflow from the control chamber to the high-pressure flow path through the throttle. 2. The accumulator type fuel injection device according to claim 1, wherein the check valve is provided inside the plate. 3. The accumulator type fuel injection device according to claim 1, wherein the check valve is a ball valve having a ball and a tapered surface for seating the ball. 4. The check valve according to claim 1, wherein a lift amount of the check valve is regulated, and the restricted lift is given a second throttle effect by the regulated lift. Accumulation type fuel injection device. 5. The accumulator type fuel injection device according to claim 1, wherein a weak urging mechanism such as a weak spring is provided behind the check valve.