JPS6165071A - Electromagnetic valve - Google Patents

Abstract

PURPOSE:To form an electromagnetic valve in a very easy way and miniaturized with increased responsiveness by providing a solenoid valve and a pool valve arranged downstream from the solenoid valve in an electromagnetic valve for stopping fuel feed. CONSTITUTION:An electromagnetic valve 8 for stopping fuel feed to a fuel injection nozzle 2 is provided. The electromagnetic valve 8 includes a solenoid valve 81 and a spool valve 82 arranged downstream from the valve 81. Feeding to an upper oil pressure chamber 824 of spool valve at high pressure is switched by the solenoid valve 81 to change the pressure within the upper oil pressure chamber 824 of spool valve and spill is controlled by moving a spool 822 up or down. Thereby, by electromagnetic valve itself can be formed in a very easy way and miniaturized, therefore its responsiveness also be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a fuel injection device for an internal combustion engine, and in particular to a normally open type solenoid valve having a spill mechanism for stopping fuel supply to a fuel injection nozzle. Regarding.

<Prior Art> In internal combustion engines, especially diesel engines, highly accurate fuel injection control is required in order to always obtain the best performance under all operating conditions. Various attempts have been proposed in order to meet this demand, and for example, the same applicant as the applicant of the present invention published an article titled "Flow Control Device and Fuel Injection Control System for Internal Combustion Engine" on June 8, 1980. Filed and published in Japanese Unexamined Patent Publication No. 5
The flow control device disclosed in Publication No. 8-214660 has a structure that combines the advantages of both the fine adjustment function of an electric on-off valve and the excellent high-speed relief function of a hydraulic on-off valve, and uses an electromagnetic relief valve. Spill is controlled by turning it on and off using a valve to stop fuel supply.

On the other hand, diesel engine fuel injection reduces fuel consumption.

The trend is toward higher pressures from the standpoint of emissions, and the spill solenoid valves that control this high-pressure fuel must also be able to cope with this high pressure (that is, electromagnetic force and responsiveness).

However, in the conventionally known solenoid valve, the solenoid must be made powerful in order to cope with high pressure, and therefore the solenoid valve must also be large in size.

<Problems to be Solved by the Invention> An object of the present invention is to provide a fuel injection device for an internal combustion engine that can cope with high pressure without increasing the capacity and has excellent responsiveness.

Means for Solving Problems> An object of the present invention is to provide a solenoid valve comprising a solenoid valve and a spool valve disposed downstream of the solenoid valve; It consists of a valve body to be moved, a solenoid valve hydraulic chamber that accommodates the valve body, a valve seat having a small hole, and a spring that biases the valve body to a normally closed state; A spool valve upper hydraulic chamber communicating with the solenoid valve hydraulic chamber through a small hole, a spool slidably housed in the spool valve upper 91S hydraulic chamber, and a spool valve lower hydraulic chamber provided below the spool. , an annular groove for a drain line provided in the lower part of the spool valve upper hydraulic chamber facing the spool, a spring that biases the spool downward, and a pump pressure chamber of a high pressure pump that connects the spool valve lower hydraulic chamber a passageway connecting the solenoid valve hydraulic chamber to the spool valve lower hydraulic chamber, and forming a restriction between the spool valve upper hydraulic chamber and the drain line annular groove; This is achieved by a solenoid valve characterized by:

That is, in the solenoid valve of the present invention, the spool valve upper hydraulic chamber is connected to the drain line annular groove by a throttle, and high pressure is supplied to the spool valve upper hydraulic chamber via the solenoid valve hydraulic chamber, and this high pressure spool valve upper hydraulic chamber is connected to the drain line annular groove. The supply to the hydraulic chamber is turned ON/OFI'l by a solenoid valve to change the pressure in the upper hydraulic chamber of the spool valve, thereby moving the spool up and down, thereby controlling spill.

It is preferable that the throttle is formed in a gap between the spool and a cylinder member constituting the spool valve upper hydraulic chamber.

Furthermore, if the cylinder member is formed into a tapered shape that expands upward, and the cross-sectional area of the gap increases as the spool rises, it is useful to improve the spillability.

<Example> The present invention will be described in detail below with reference to the accompanying drawings showing examples of the solenoid valve of the present invention.

FIG. 1 shows an embodiment of the solenoid valve of the present invention. Reference numeral 1 denotes a high-pressure pump, and as the high-pressure pump 1, a distribution type pump that is normally used as an injection pump is used, but the governor and timer attached to the high-pressure pump may not be provided. The plunger 11 of the high-pressure pump 1 is driven by an engine (not shown), and rotates and reciprocates synchronously with two rotations of the engine. The first notch groove 12 of the plunger 11 is connected to the cylinder 1.
The time when the plunger 11 is in communication with the suction port 14 of No. 3 is the suction stroke, and the plunger 11 sucks fuel oil into the pressure chamber 131 formed by the cylinder 13 and the tip member of the plunger 11 while moving to the left in the figure. . The discharge stroke is when the second notch groove 15 of the plunger and the discharge port 16 of the cylinder 13 are in communication with each other, and the plunger 11 moves to the right in the figure to discharge fuel oil from the pressure chamber 131. Notch 't115
, and is delivered to the high pressure line 18 via the discharge port 16. The time when the plunger 11 starts to move to the right is sufficiently earlier than the time when the injection nozzle 2 is requested to start injection, and the time when the plunger 11 stops moving to the right is when the injection nozzle 2 is requested to stop injection. A fixed time is given that is sufficiently later than the time.

Due to the action of the high pressure pump l, the discharge port 1 of the cylinder 13
Fuel discharged from 6 is supplied to injection nozzle 2 via high pressure line 18. The pressure in the pressure chamber 131 is controlled by the solenoid valve 8 of the present invention as described below.

The solenoid valve 8 is composed of a solenoid valve 81 as an electric on-off valve and a spool valve 82 as a hydraulic on-off valve.

The spool valve 82 includes a cylinder member 821 and a spool 822.
, spring 823. Spool 822
has a cylindrical shape, and is fitted into the cylinder member 821 so as to be able to slide vertically as shown in FIG. A chamber 825 is formed. Lower hydraulic chamber 825 is pressure chamber 1
It is directly connected to 31.

There is a gap 826 (0.3flφ) on the outer peripheral surface of the spool 822.
An annular groove (equivalent to a throttle) is formed between the cylinder member 821 and the upper hydraulic chamber 824 and an annular groove 827 formed on the inner circumferential surface of the cylinder member 821 through this gap 826 . A spring 823 is provided within the upper hydraulic chamber 824, and this spring force then presses the spool 822 downward. The hydraulic pressure in the lower hydraulic chamber 825 is transferred to the upper hydraulic chamber 82.
4, the spool 822 moved upward against the spring 823, and the left end surface 822b of the spool 822 overlapped with a part of the annular groove 827 formed on the inner peripheral surface of the cylinder member 821. time, lower hydraulic chamber 825
The fuel in the tank flows through this annular groove 827 to the drain line 7.
It is relieved by 1.

Fuel is supplied to and stopped from the upper hydraulic chamber 824 by the solenoid valve 81 . The solenoid valve 81 has a small hole 813 (in the embodiment shown in FIG. 1) that has a sufficiently large cross-sectional area with respect to the solenoid 811, the valve body 812, and the gap 826 (equivalent to 0.3 fiφ in the embodiment shown in FIG. 1). 0.70φ), a stopper 815 that restricts the stroke of the valve body 812, a spring 816 that maintains the valve body 812 in a normally closed state, and a solenoid valve hydraulic chamber 817 that houses the valve body 812. . This hydraulic chamber 817 communicates with the pressure chamber 131 via a passage.

When the solenoid 811 is de-energized, the valve body 812 is in a closed state, that is, the small hole 813 is closed.

Therefore, the fuel in the upper hydraulic chamber 824 is relieved to the annular groove 827 and the drain line 71 via the gap 826.

When the solenoid 811 is energized, the valve body 812 opens and the fuel in the solenoid valve hydraulic chamber 817 flows into the upper hydraulic chamber 824 through the small hole 813.

The computer 20 energizes the solenoid 811 . The computer 20 energizes the solenoid 811 at an appropriate time and for an appropriate period in accordance with signals such as the accelerator opening degree α and the pump rotation speed N.

Next, the basic operation of the solenoid valve 8 shown in FIG. 1 will be explained below with reference to FIGS. 2a to 2C.

(a) At the start of nil injection and during the injection period, the computer 20 energizes the solenoid 811),
As a result, the valve body 812 is drawn upward by the suction force of the solenoid 811, and the small hole 813 is opened. Therefore, the fuel pressure in the pressure chamber 131 is transferred to the upper hydraulic chamber 824 from the passage 81.
8. Acts through pressure chamber 817. For this reason, spool 8
The pressure is balanced between the top and bottom of 22, but since it is pressed downward by the spring force, the spool 822 is closed, and the fuel discharged from the high pressure pump 1 flows through the notch groove 15 and the high pressure inlet 18. It is supplied to the injection nozzle 2 (see FIG. 2a).

(b) At the end of injection, the computer 20 stops energizing the solenoid 811. As a result, the valve body 812 is closed by the force of the spring 816 and closes the small hole 813.

Since the fuel supply to the upper hydraulic chamber 824 is stopped, the fuel in the upper hydraulic chamber 824 passes through the gap 826 and flows into the annular groove 827.
, the drain line 71 is relieved. For this reason, the oil pressure in the upper hydraulic chamber 824 decreases, and the pressure balance between the upper and lower portions of the spool 822 is disrupted (see FIG. 2b).

[C) The spool 822 is raised by the hydraulic pressure of the lower hydraulic chamber 825 against the force of the spring 823, and when the annular groove 827 of the cylinder member 821 and the end face of the spool 822 communicate with each other, most of the fuel is transferred to the lower hydraulic pressure. chamber 825, annular 48
27, pump low pressure chamber 72 via drain line 71
A large amount of main relief is carried out (second
(see figure c).

As described above, in the solenoid valve 8 of the present invention, the spool 822 is displaced by opening and closing the small hole 813, and a large amount of fuel can be instantly relieved. What is important here is that the minimum passage area of the small hole 813 must be larger than the minimum passage area of the gap 826. As previously mentioned, in the embodiment shown in FIG.
+nφ equivalent, and the small hole 813 is equivalent to 0.71111φ. Since fuel is constantly being relieved from the gap 826, when the valve body 812 is opened, the upper hydraulic chamber 82
This is because in order to increase the pressure of No. 4, it is necessary to supply more fuel than the amount of relief that is constantly being relieved. Note that if the gap 826 is equal to or larger than 0.5 flφ, the injection amount per stroke will be significantly reduced in the low speed range, which is not preferable.

In the embodiment of the solenoid valve of the present invention shown in FIG. 1, there is a gap 826 between the spool 822 and the cylinder member 821.
(equivalent to 0.30φ), but as shown in FIG. 3, the spool 8
A similar effect can be obtained by providing a diaphragm 826' (0.3 mm φ) passing through 22.

Furthermore, in the embodiment shown in FIG. 1, a gap 826 having a constant gap is formed between the spool 822 and the cylinder member 821, but as shown in FIG. , the gap 826'' may be configured to widen as the spool 822 rises.If the gap is configured in this way, the spool 822 rises at an accelerated rate, which helps improve spillability.

<Effects of the Invention> Since the solenoid valve of the present invention uses a spool as described above, the spool can be removed simply by making the minimum passage area of the small hole larger than the minimum passage area of the gap between the spool and the cylinder member. A large amount of fuel can be instantly relieved by displacement. Therefore, the passage area of the small hole can be made very small, and therefore the suction force when the solenoid opens the valve can be made as small as possible. This means that even when the fuel injection pressure is increased, the solenoid valve itself can be formed extremely simply and compactly, and a solenoid valve with excellent responsiveness can be obtained.

Thus, the electromagnetic valve of the present invention can open and close the spool capable of producing a large amount of spill by controlling the hydraulic pressure applied to the upper end surface of the spool with an electric on-off valve, and control the fuel pressure in the injection pump pressure chamber. It can be used for electronic control of injection.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the solenoid valve of the present invention. 2a, 2b, and 2c are schematic vertical sectional views illustrating the operation of the solenoid valve shown in FIG.
The figures are schematic longitudinal cross-sectional views at the start of injection and during the injection period, Fig. 2b at the end of injection, and Fig. 2c when the spool is raised. FIG. 3 is a schematic longitudinal sectional view showing another embodiment of the solenoid valve of the present invention. FIG. 4 is a schematic vertical sectional view showing still another embodiment of the solenoid valve of the present invention. ■-High pressure pump, 2--Injection nozzle, 8-Solenoid valve, 81- Solenoid valve, 82- Spool valve, 131--Pressure chamber, 811--Solenoid,
812-m-valve body, 813-・small hole, 81
4--Valve seat, 816, 823--Spring, 817--Solenoid valve hydraulic chamber, 818--Passage, 822--Spool, 8
24...-Spool valve upper hydraulic chamber, 825-Spool valve lower hydraulic chamber, 826, 826', 826'-Gap, 827-
Annular groove for drain line. Figure 20 Figure 3 Figure 4

Claims (3)

[Claims] 1. A solenoid valve comprising a solenoid valve and a spool valve disposed downstream of the solenoid valve; the solenoid valve comprising a solenoid, a valve body that is moved up and down by the solenoid, and a solenoid valve hydraulic chamber that houses the valve body. , a valve seat having a small hole, and a spring that biases the valve body to a normally closed state; a spool valve upper hydraulic chamber in which the spool valve communicates with a solenoid valve hydraulic chamber through a small hole in the solenoid valve; a spool slidably housed in the spool valve upper hydraulic chamber, a spool valve lower hydraulic chamber provided below the spool, and a spool provided facing the spool at the lower part of the spool valve upper hydraulic chamber. an annular groove for the drain line; a spring that urges the spool downward; and an opening that opens the spool valve lower hydraulic chamber toward the pump pressure chamber of the high-pressure pump; A solenoid valve characterized in that a passage connected to a lower hydraulic chamber of the spool valve is provided, and a restriction is formed between the upper hydraulic chamber of the spool valve and an annular groove for a drain line. 2. 2. The electromagnetic valve according to claim 1, wherein the throttle is formed by a gap between the spool and a cylinder member constituting the spool valve upper hydraulic chamber. 3. 3. The electromagnetic valve according to claim 2, wherein the cylinder member is formed in a tapered shape that expands upward, and the cross-sectional area of the gap increases as the spool rises.