GB1598721A - Fuel injection nozzle for internal combustion engines - Google Patents

Description

(54) FUEL INJECTION NOZZLE FOR INTERNAL COMBUSTION ENGINES (71) We, ROBERT BOSCH GMBH, a Germany company of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to fuel injection nozzles having a plurality of injection passages opening therefrom.

In known fuel injection nozzles of this type, the differing angles of inclination of the injection passages are used in order to supply different specific sectors of the combustion chamber with fuel. The requirement with respect to the differing angles generally ensues from the sloping position in which the fuel injection nozzle is fitted into the engine. The quantity of fuel injected to the different specific sectors is also of importance, in addition to the direction of injection. Thus, the quantity of fuel and the direction of injection are in each case adapted to engine data such as the shape of the combustion chamber, the position of the nozzle and the air circulation etc. They have a decisive effect upon the ignition, the travel hardness,fuel consumption and the composition of the exhaust gas.

It is also known that the branching-off point of the injection orifice in the terminal bore influences the distribution of the quantity of fuel, since the fuel pressure is at a maximum at the bottom of the terminal bore and decreases towards the inlet, that is in the region of the valve seat. Therefore, in a known fuel injection nozzle, the diameter of the injection orifices in the region of the valve seat is chosen to be larger than that of the injection orifices arranged in the bottom of the terminal bore. This results in a more uniform distribution of the quantity of fuel to be injected. However the choice of different diameters has the disadvantage that uneven wear of the orifices ensues, thus causing variation of the injected quantities from nozzle to nozzle, particularly over a period of time.It is an object of this invention to solve this problem or at least reduce its severity.

In accordance with this invention there is provided a fuel injection nozzle for internal combustion engines comprising a nozzle body which receives a valve needle, said valve needle being provided with a valve cone which co-operates with a valve seat of the nozzle body so as to define between the valve needle and the nozzle body a terminal bore, said terminal bore having injection passages for communication with the cylinder of the internal combustion engine, said injection passages having differing, but specific, directions of fuel injection and each having a longitudinal axis, in the direction of which axis the fuel flows through the passage, said axis substantially intersecting the longitudinal axis of the terminal bore to create therebetween an angle which defines the angle of inclination of the passage from the starting point at the base of the terminal bore to its position in the terminal bore, said injection passages opening into the terminal bore through their apertures and being in communication with the terminal bore at all times, said passages and apertures being arranged such that the angles of inclination of passages with apertures nearer the valve cone are smaller than the angles of inclination of passages further away from the valve cone.

By virtue of the non-uniform pressure within the terminal bore the flow through those passages adjacent the base of the terminal bore will be greater than if those passages were nearer the valve cone. By making the angle of inclination of the passages nearer the valve cone smaller than the angle of inclination of the passages further away from the valve cone, the pressure effect is partly countered.

In contrast to the prior construction, the fuel injection nozzle in accordance with this invention has the advantage of obtaining controlled distribution of the quantities of fuel by correlating the branching-off points of the injection passages with the respective angles of inclination thereof. An additional advantage resides in reducing the variation of the injected quantities from nozzle to nozzle, particularly over a long period of time, since these injection passages are all of the same diameter. By virtue of the invention therefore, and despite unavoidable manufacturing tolerances, there are only slight differences in the distribution of the quantities of fuel by the injection passages.

and thus in the total flow-through quantity from nozzle to nozzle, and there is only a negligible change in the error even when the nozzle is in operation for a long period of time.

The invention will be further described hereinafter, by way of example with reference to the accompanying drawings, in which: Figures 1 and 3 are sections through known fuel injection nozzles; Figures 2 and 4 are the corresponding function graphs of these known nozzles, and Figure 5 is a section through one embodiment of the present invention.

Figures 1, 3 and 5 are each a longitudinal section through the portion of a fuel injection nozzle incorporating the injection passages. In all three Figures, a valve seat 2 is disposed in a nozzle body 1, and the valve cone 3 of a valve needle 4 abuts against the valve seat 2. Fuel flows under pressure from a fuel injection pump (not illustrated) into a pressure chamber (not illustrated) which is disposed between the valve needle 4 and the nozzle body 1 and which the fuel acts, in the opening direction, upon pressure shoulders 5 (only partially illustrated) disposed on the valve needle 4. Furthermore, the nozzle body 1 incorporates a terminal bore, defined between the valve cone when in the closed position and the nozzle body, and from which bore branch injection passages 7. The terminal bore 6 is covered by the valve cone 3.

When the fuel fed is under adequate pressure, the value needle 4 is displaced against a closing force (not illustrated), generally that of a closure spring, so that the fuel can flow from the pressure chamber, passed the valve seat 2, and into the terminal bore 6 and then into the combustion chamber by way of the injection passages 7.

Since injection passages act as throttles, their diameters and their lengths directly affect the quantity of fuel flowing through.

In the case of a plurality of injection passages, their diameters and lengths directly affect the distribution of fuel to the individual injection passages. The quantity of fuel delivered through each injection passage is also affected by the point at which the injection passages commence in the terminal bore because the pressure distribution in the terminal bore is non-uniform, the maximum pressure prevailing in the bottom of the terminal bore, and the lowest pressure prevailing in the vicinity of the valve seat. Thus, the point at which an injection passage commences in the terminal bore 6 has a direct influence on the distribution of the quantity of fuel flowing through the injection passages.

The quantity of fuel delivered through each injection passage is also affected by the angle which the axis of the passage forms with the axis of the terminal bore. This angle is measured upwardly from the central axis of the terminal bore to the axis of the orifice, for instance al or a2 in Figure l.

The greater this angle is, the greater is the resistance formed by flow deflection. Thus this angle also has a direct influence on the distribution of fuel.

A conventional fuel injection nozzle is illustrated in Figure 1 in which the axis of an injection passage 7' forms a large angle al with the axis of the terminal bore, and the axis of the second injection passage 7" forms a relatively small angle a2. Conventionallv, the axes of the two injection passages and the axis of the terminal bore have a common point M of intersection. Since the injection passage 7" branches off substantially in the bottom of the terminal bore, the pressure prevailing upstream of its inlet is relatively high, while a lower pressure prevails upstream of the injection passage 7', apart from the fact that the direction of the injection passage constitutes an additional flow resistance.

Conditioned by this arrangement of the injection passages, the distribution of the quantities of fuel is as shown in Figure 2.

Two injection passages 7' and two injection passages 7" are provided in each case.

The quantity of fuel flowing out through each injection passage 7" is 5% greater than a quarter of the total quantity, while the quantity flowing through each injection passage 7' is 5% smaller than the average quantity. This quantity distribution corresponds approximately to the requirements of the engine, since the injection nozzle is arranged off-centre relative to the combustion chamber.

In the nozzle illustrated in Figure 3, in contrast to the nozzle illustrated in Figure 1, the terminal bore 6 has been shortened bv approximately half. The reduction in the size of the terminal bore is a fundamental tendency in the construction of fuel injec tion nozzles in order thereby to reduce to a minimum the residual volume remaining below the valve seat 2. This residual volume acts as a dead space, since it communicates with the combustion chamber by way of the injection passages 7. Experience has shown that this dead volume (including the volumes of the injection passages) is substantially proportional to the emission of hydrocarbons.A measurement graph, plotted with reference to this nozzle, is illustrated in Figure 4 and shows that, with a reduction in the size of the terminal bore, the distribution of the delivery quantity to the individual injection passages becomes more unfavourable, namely in a greater ratio than that in which the size of the dead space is reduced. Thus, an unacceptably small quantity emerges through the injection orifices 7' in the case of an extremely small dead space.

The injection orifices should primarily atomize, and thus prepare the fuel.

In the embodiment of the invention which is illustrated in Figure 5, and in which the terminal bore has been reduced to a size corresponding to Figure 3, the diameters of the two injection passages 7 are equal.

However, the injection passage 7" has been displaced upwardly and parallel, whereas the injection passage 7' has been displaced downwardly and parallel, so that the latter commences adjacent the bottom of the terminal bore. The quantity distribution is again shown in Figure 2 on the basis of this arrangement of the injection passages 7' and 7" relative to one another and with respect to the terminal bore 6, that is, corresponding to the requirement of the engine, with a minimum of dead space.

The invention is not only limited to this embodiment, but also relates to correlations of injection passages with the terminal bore and their diameters, by means of which controlled distribution of the fuel is to be effected with corresponding fuel preparation. The determining factor of the invention is that the injection passages having axes forming a large angle with the axis of the terminal bore are displaced more towards the bottom of the terminal bore, whereas the injection passages having axes forming a smaller angle with the axis of the terminal bore are displaced more towards the valve seat, with a minimum of dead space. Thus, it is possible to dispense with the type of quantity correction frequently chosen, namely different diameters of the injection passages.

WHAT WE CLAIM IS: 1. A fuel injection nozzle for internal combustion engines comprising a nozzle body which receives a valve needle, said valve needle being provided with a valve cone which co-operates with a valve seat of the nozzle body so as to define between the valve needle and the nozzle body a terminal bore, said terminal bore having injection passages for communication with the cylinder of the internal combustion engine, said injection passages having differing, but specific, directions of fuel injection and each having a longitudinal axis, in the direction of which axis the fuel flows through the passage, said axis substantially intersecting the longitudinal axis of the terminal bore to create therebetween an angle which defines the angle of inclination of the passage from the starting point at the base of the terminal bore to its position in the terminal bore, said injection passages opening into the terminal bore through their apertures and being in communication with the terminal bore at all times, said passages and apertures being arranged such that the angles of inclination of passages with apertures nearer the valve cone are smaller than the angles of inclination of passages further away from the valve cone.

2. A fuel injection nozzle substantially as hereinbefore described with reference to, and as illustrated in Figure 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. tion nozzles in order thereby to reduce to a minimum the residual volume remaining below the valve seat 2. This residual volume acts as a dead space, since it communicates with the combustion chamber by way of the injection passages 7. Experience has shown that this dead volume (including the volumes of the injection passages) is substantially proportional to the emission of hydrocarbons. A measurement graph, plotted with reference to this nozzle, is illustrated in Figure 4 and shows that, with a reduction in the size of the terminal bore, the distribution of the delivery quantity to the individual injection passages becomes more unfavourable, namely in a greater ratio than that in which the size of the dead space is reduced.Thus, an unacceptably small quantity emerges through the injection orifices 7' in the case of an extremely small dead space. The injection orifices should primarily atomize, and thus prepare the fuel. In the embodiment of the invention which is illustrated in Figure 5, and in which the terminal bore has been reduced to a size corresponding to Figure 3, the diameters of the two injection passages 7 are equal. However, the injection passage 7" has been displaced upwardly and parallel, whereas the injection passage 7' has been displaced downwardly and parallel, so that the latter commences adjacent the bottom of the terminal bore. The quantity distribution is again shown in Figure 2 on the basis of this arrangement of the injection passages 7' and 7" relative to one another and with respect to the terminal bore 6, that is, corresponding to the requirement of the engine, with a minimum of dead space. The invention is not only limited to this embodiment, but also relates to correlations of injection passages with the terminal bore and their diameters, by means of which controlled distribution of the fuel is to be effected with corresponding fuel preparation. The determining factor of the invention is that the injection passages having axes forming a large angle with the axis of the terminal bore are displaced more towards the bottom of the terminal bore, whereas the injection passages having axes forming a smaller angle with the axis of the terminal bore are displaced more towards the valve seat, with a minimum of dead space. Thus, it is possible to dispense with the type of quantity correction frequently chosen, namely different diameters of the injection passages. WHAT WE CLAIM IS:

1. A fuel injection nozzle for internal combustion engines comprising a nozzle body which receives a valve needle, said valve needle being provided with a valve cone which co-operates with a valve seat of the nozzle body so as to define between the valve needle and the nozzle body a terminal bore, said terminal bore having injection passages for communication with the cylinder of the internal combustion engine, said injection passages having differing, but specific, directions of fuel injection and each having a longitudinal axis, in the direction of which axis the fuel flows through the passage, said axis substantially intersecting the longitudinal axis of the terminal bore to create therebetween an angle which defines the angle of inclination of the passage from the starting point at the base of the terminal bore to its position in the terminal bore, said injection passages opening into the terminal bore through their apertures and being in communication with the terminal bore at all times, said passages and apertures being arranged such that the angles of inclination of passages with apertures nearer the valve cone are smaller than the angles of inclination of passages further away from the valve cone.

2. A fuel injection nozzle substantially as hereinbefore described with reference to, and as illustrated in Figure 5 of the accompanying drawings.