Injection Installation for Diesel Internal Combustion Engine

The present invention relates to an injection installation for a Diesel internal combustion engine which essentially includes an injection pump with injection lines, injection valves with valve needles or pins opening inwardly against spring pressure and leakage oil lines starting from the injection valves.

With injection systems of this type, the valve needle or pin again moves back toward its seat at the end of the injection operation. It thereby displaces a volume which results from the needle cross section and the needle stroke.

This volume which is pumped by the valve needle with the force of the nozzle spring, is sprayed off in part through the nozzle openings and is pumped in part into the injection line. The volume sprayed off through the nozzle openings leaves only with relatively low velocity. This brings about a lengthening of the injection and a poor atomization so that an unfavorable development of the combustion process results in the engine. The volume pumped into the injection line produces thereat a pressure wave which moves toward the injection pump, is reflected thereat, and moves back toward the injection valve and, under certain circumstances, causes an after-injection at the injection valve. However, an after-injection will also affect unfavorably the combustion process.

The present invention is now concerned with the task to eliminate the described disadvantages. The underlying problems are solved according to the present invention in that an installation consisting of a sensor detecting the direction of flow and of a discharge valve is arranged in each injection line, preferably in proximity of the injection valve, which conducts away into the leakage oil line the pump volume of the injection valve resulting at the end of the injection operation.

The injection period is kept short by the present invention combined with a good atomization of the fuel. An after-injection of the injection valves does not take place. As soon as fuel flows in the direction toward the injection pump, the discharge valve in proximity of the injection valve is opened, and the fuel which flows back is conducted away into a space with low pressure. Since this is the path of least resistance for the volume pumped by the nozzle needle, practically hardly any fuel still flows through the nozzle apertures in the injection valve and into the injection line. The flow direction is thereby determined by the flow direction sensor in proximity of the injection valve which then controls the discharge valve.

The discharge valve may consist advantageously of a valve body closing in the direction toward the injection pump and opening thereby in the direction toward the leakage oil line.

According to another embodiment of the present invention, the flow-direction sensor and the discharge valve may be arranged in parallel to one another. However, it is also possible to combine the flow-direction sensor and the discharge valve into a structural unit. The check valve may thereby be arranged at or in the valve body of the discharge valve. If a throttle is used as sensor for detecting the direction of flow, then the throttle may be provided at the valve body of the discharge valve.

Accordingly, it is an object of the present invention to provide an injection installation for a Diesel internal combustion engine which avoids by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in an injection system for a Diesel internal combustion engine which ensures a short injection period accompanied with good atomization of the fuel.

A further object of the present invention resides in an injection installation for a Diesel internal combustion engine which results in an improved combustion process.

Still a further object of the present invention resides in an injection installation for Diesel internal combustion engines which precludes an after-injection that might unfavorably affect the combustion process.

Another object of the present invention resides in an injection installation for Diesel internal combustion engines which achieves the aforementioned aims and objects by simple means that can be realized with relatively small expenditures.

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIG. 1 is a schematic view of the over-all arrangement of the injection installation in accordance with the present invention;

FIG. 2 is a schematic view of one embodiment of an injection installation in accordance with the present invention in which a sensor detecting the direction of flow is arranged in parallel with a discharge valve provided with a radial discharge into the oil leakage line;

FIG. 3 is a schematic view of an injection installation according to the present invention, similar to FIG. 2, in which the discharge into the oil leakage line takes place in the axial direction of the discharge valve;

FIG. 4 is a schematic view, partly in cross section, through a modified embodiment of an injection installation in accordance with the present invention equipped with a flow-direction sensor in the valve body of a discharge valve and with a radial discharge into the oil leakage line; and

FIG. 5 is a schematic view, partly in cross section, through an injection installation in accordance with the present invention similar to FIG. 4, with an axial discharge from the discharge valve into the oil leakage line .

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, the injection installation illustrated in FIG. 1 consists of a conventional injection pump 1, by means of which fuel is fed to an injection valve generally designated by reference numeral 3 by way of injection lines 2. The injection valve 3 essentially consists of a valve housing 4 with a nozzle opening 5 and of a valve needle or pin 6 which is lifted off its valve seat, opening in the inward direction, by the fuel supplied under pressure by the injection pump 1 against the action of a compression spring 7 so that the fuel is discharged out of the injection valve 3 through the nozzle aperture 5. A leakage oil line 8 is connected to the valve housing 4 which conducts leakage oil either to the inlet side of the injection pump 1 or into a reservoir tank.

In order to avoid that the volume in fuel which is displaced at the end of each injection by the nozzle needle during its movement toward the valve seat, is sprayed off or discharged in part through the nozzle aperture 5 and is pumped back in part into the injection line 2, a conventional flow-direction sensor 9 and a discharge valve 10 are provided in the injection line 2 in proximity of the injection valve 3 and in a parallel arrangement to one another. The discharge valve 10 is connected with the leakage oil line 8 by way of a line 11.

The flow-direction sensor 9 permits fuel to flow unimpairedly in the injection line 2 in the direction of arrow 12, but blocks the injection line 2 when the pressure in the fuel between the injection valve 3 and the flow-direction sensor 9 is larger than in the injection line 2 between the flow-direction sensor 9 and the injection pump 1. The discharge valve 10 closes the injection line 2 and the line 11 during the injection operation. During the return flow of the fuel out of the injection valve 3, it enables a discharge through the line 11.

As can be seen from FIGS. 2 and 3, the flow-direction sensor 9 may be constructed as ball check-valve, and the discharge valve 10 may consist of a cylindrical valve body with a conical valve seat. The line 11 may be connected radially with the discharge valve 10 according to FIG. 2 and may be connected axially with the discharge valve 10 according to FIG. 3. Possibly, the valve bodies may also be stressed with compression springs. However, it is also possible to utilize a ball-shaped valve body for the discharge valve.

In the embodiments according to FIGS. 4 and 5, the flow-direction sensor forms together with the discharge valve a structural unit. The flow-direction sensor detecting the direction of flow is represented by throttle bores 13 in a valve body 14 forming the discharge valve. During the injection operation, the valve body 14 keeps the line 11 closed. Fuel under pressure passes through the throttle bores 13 and reaches through the valve body 14 the injection valve. Fuel flowing back after the termination of the injection operation lifts the valve body 14 so that the valve body 14 closes the injection line 2 at the feed line and opens the line 13. Possibly the valve body may also be constructed spring-loaded. It is additionally possible to represent the valve body as a ball and to form a throttling place by means of the gap between the ball and the valve housing. According to FIG. 4, the discharge into the line 11 takes place out of the structural unit in the radial direction whereas according to FIG. 5 it takes place in the axial direction.

In lieu of the throttle bores 11, also ball check-valves may be installed into the valve body 14.

Possibly, the injection valve 3 together with the flow-direction sensor 9 and the discharge valve 10 may also be constructed as a structural unit.

The fuel quantity controlled by the discharge valve 10 may be conducted also into a reservoir in lieu of into the leakage oil line 8 and may be subsequently conducted back to the injection line possibly throttled.

While I have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.