WO2014206606A1

WO2014206606A1 - Control valve

Info

Publication number: WO2014206606A1
Application number: PCT/EP2014/058919
Authority: WO
Inventors: Dominik Kuhnke
Original assignee: Robert Bosch Gmbh
Priority date: 2013-06-25
Filing date: 2014-04-30
Publication date: 2014-12-31
Also published as: EP3014100B1; EP3014100A1; CN105492755A; CN105492755B; DE102013212140A1

Abstract

The invention relates to a control valve for a fuel injector, in particular a common-rail fuel injector, comprising a valve piece (1) having an outflow opening (3) which is formed inside a valve seat (2) formed as a flat seat, and a reciprocating valve-closing element (4) which interacts in a seal-forming fashion with the valve seat (2). According to the invention, the outflow opening (3) is embodied in a slit shape and has a length (L) which is greater than a width (B), wherein the length (L) corresponds essentially to a diameter (D) or a radius (R) of a circular surface (5), within which the outflow opening (3) and at least one further outflow opening (6, 6') which is connected to the outflow opening (3) and/or separated from the outflow opening (3) are arranged. The invention also relates to a fuel injector having a control valve of said type.

Description

description

title

control valve

The invention relates to a control valve for a fuel injector, in particular a common rail fuel injector, with the features of the preamble of claim 1. Furthermore, the invention relates to a fuel! Njektor with such a control valve.

State of the art

Control valves of the aforementioned type are regularly used in fuel injectors, which have a hubbewegliche nozzle needle for releasing and closing at least one injection port. The control valve serves to control the lifting movement of the nozzle needle. Opens the control valve, a control chamber is relieved, so that acting in the closing direction of the nozzle needle control pressure decreases in the control chamber and opens the nozzle needle. The actuation of the control valve is generally carried out by means of an actuator, such as a Magnetaktors or a

Piezoelectric actuator.

German Offenlegungsschrift DE 10 2006 049 050 A1 exemplifies a fuel injector with a control valve for actuating an injection valve member which releases or closes off at least one injection opening. For this purpose, the control valve comprises a liftable valve piston, which cooperates sealingly with a valve seat designed as a flat seat. If the valve piston is sealingly seated on the flat seat, a control pressure which acts on the injection valve member in the closing direction builds up in the control chamber. Upon actuation of the control valve by means of an electromagnet, the valve piston lifts off the valve seat and a connection of the control chamber is made with a low pressure area. As a result, the control pressure in the control chamber and thus the injection valve member acting in the closing direction decreases Force. The injection valve member opens and releases the at least one injection opening in this way. The provision of the valve piston takes place by means of the spring force of a spring after completion of the energization of the electromagnet. This in turn results in the increase of the control pressure in the control chamber, so that also the injection valve member is returned to its sealing seat and the at least one injection port closes again.

For the representation of partial injections, a fast-switching control valve is advantageous in order to bring about rapid relief of the control chamber. The advantage here is a reduced stroke of the liftable closing element of the control valve. At the same time, however, a sufficiently large outflow cross-section must be ensured. To ensure this, the diameter of a discharge opening located within the valve seat can be increased. However, this also increases the valve closing element formed on the surface, which comes to lie within the diameter of the valve seat, and is acted upon in the closed position of the control valve by the control pressure of the control chamber. The result is an increase in the force acting on the valve closing element in the opening direction hydraulic force. This can be counteracted by the spring force of a spring is increased, which acts on the valve closing element in the closing direction. To open the valve but then larger magnetic forces are required, which in turn adversely affects the switching time of the control valve.

Based on the above-mentioned prior art, the present invention has the object to provide a fast-switching control valve for a fuel injector, which has at least one optimized in terms of reduced switching forces and / or low strokes discharge opening. Furthermore, a control valve with an increased life is to be provided.

To solve the problem, the control valve with the features of claim 1 is proposed. Advantageous developments of the invention can be found in the dependent claims. Furthermore, a fuel! Njektor specified with such a control valve. Disclosure of the invention

The proposed control valve comprises a valve piece with a discharge opening formed inside a valve seat designed as a flat seat, and a lift-movable valve closing element sealingly cooperating with the valve seat. According to the invention the outflow opening is slit-shaped and has a length L which is greater than a width B. The length L corresponds essentially to a diameter D or a radius R of a circular area within which the outflow opening and at least one further outflow opening connected to the outflow opening and / or separate from the outflow opening are arranged.

The slot-shaped outlet opening has in comparison to a circular

Outflow opening on the advantage that it has a large outflow circumference at the same time small area. Accordingly, the valve closing element is subjected to a smaller hydraulic force via the slot-shaped outflow opening, with the same outflow circumference, so that the shifting forces can be reduced. Alternatively or additionally, the stroke of the valve closing element can be reduced because a fast discharge of the control chamber is ensured via the outflow circumference.

However, an unfavorable length / width ratio (L / B >> 1) of the slit-shaped outflow opening can lead to stresses in the valve piece which occur in particular at the ends in the longitudinal direction of the outflow opening (notch stress). To reduce the voltages is therefore proposed within a slot-shaped

Outflow opening receiving circular surface form at least one further outflow opening. The at least one further outflow opening can be connected to the slot-like outflow opening or formed as a separate outflow opening. It has been found that the load on the valve piece can be reduced by this measure. This in turn leads to an increase in the service life of the control valve.

According to a preferred embodiment of the invention, the at least one further outflow opening is likewise slot-shaped and has a longitudinal axis A ', which is inclined relative to a longitudinal axis A of the first slot-shaped outflow opening. In In a particularly preferred embodiment, a plurality of slit-like

Outflow openings arranged in a cross or star shape. The arrangement may be such that two or more slit-like outflow openings intersect.

The strength-increasing effect is achieved by avoiding a voltage-generating widening of the slit-shaped outlet openings, since in the vicinity of other pressure-loaded slots by the expansion of a supporting effect on the highly loaded notch radius is achieved. The effect can already be detected by arranging a further slot-like outflow opening within the circular area predetermined by the first outflow opening.

Alternatively or additionally, it is proposed that the at least one further outflow opening is arranged at one end of the slot-like outflow opening within the circular area. The further discharge opening arranged at the end leads to an enlargement of the notch radius, so that a stress relief is achieved.

The arranged at one end of the slit-shaped outlet opening further

Outflow opening may for example be circular and have a diameter d which is greater than the width B of the slot-like outflow opening. When determining the diameter d, however, it should be noted that the ratio surface / outlet circumference is not significantly deteriorated to the above-mentioned advantages of a slit-shaped outlet opening relative to a circular

To get outflow opening.

Alternatively, the further outflow opening arranged at one end of the slot-shaped outflow opening can be slot-shaped and have an arcuate course. Also by this measure, a stress relief is achieved by increasing the notch radius. At the same time, the further outflow opening has an optimized geometry. The arcuate course ensures the arrangement of the further slot-shaped outflow opening within the specified circular area. The effect of the voltage reduction is here in particular in the approximation to the voltage-ideal circular shape with internal pressure. An arcuate course of the further outflow opening, which is offset slightly inwards relative to the circular shape, proves to be particularly advantageous with regard to the avoidance of notch stresses. Preferably, therefore, the arcuate course of the further outflow opening follows the shape of an ellipse with two half-axes a, b, wherein the shorter half-axis a with the length L of the slit-like outflow opening defining the circular area coincides. Within the approximate circular shape thus an approximately hydrostatic stress state, so that stresses occur substantially only radially outward of the arcuate course, where they are much smaller due to the large radius.

Preferably, the half-axis a is less than a quarter of the length L of the slot-like outflow opening, at the end of which it is arranged. By this measure, a sufficient mechanical strength of the valve piece is further ensured.

Further preferably, the half-axis ratio a / b is 0.8 to 0.9. This ensures that in the case of a plurality of slit-shaped outflow openings, which are each arranged at one end of a slit-shaped radially extending outflow opening and have a curved course, a sufficient web width remains in order not to jeopardize the mechanical strength of the valve piece.

In a further development of the invention, it is proposed that the valve seat formed as a flat seat is released and is formed by at least one web, which follows an outer contour of an outflow opening. The discharge opening is therefore limited by the web. Due to the release, the fluid exiting via the outflow openings can flow off almost without pressure. As a result, an additional opening force acting on the valve closing element is avoided. In addition, depending on the particular web width selected, the sealing surface of the valve seat is reduced, so that an improved sealing effect is achieved. Because the advantages of the specified control valve, especially when used in a

Fuel! come to fruition, a fuel injector is proposed with a control valve according to the invention also. The control valve is preferably used to control the lifting movement of a nozzle needle of the fuel injector. Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

1 shows a longitudinal section through a fuel injector with a control valve according to the invention,

2 shows a plan view of a valve piece of a control valve according to the invention according to a first preferred embodiment of the invention,

3 is a plan view of a valve piece of a control valve according to the invention according to a second preferred embodiment of the invention,

FIG. 4 shows a plan view of a valve piece of a control valve according to the invention according to a third preferred embodiment of the invention,

5 is a plan view of a valve piece of a control valve according to the invention according to a fourth preferred embodiment of the invention,

FIG. 6 shows a plan view of a valve piece of a control valve according to the invention according to a fifth preferred embodiment of the invention,

FIG. 7 shows a plan view of a valve piece of a control valve according to the invention according to a sixth preferred embodiment of the invention,

8 is an enlarged view of the geometry of the outflow openings of the embodiment of FIG. 6, FIG.

9 shows a further plan view of the valve piece of FIG. 6, showing the stresses occurring in the valve piece, FIG.

FIG. 10 shows a perspective sectional view of the valve piece of FIG. 6,

11 shows a longitudinal section through a valve piece of a control valve according to the invention and Figure 12 is a partial plan view of a valve piece of a control valve according to the invention.

Detailed description of the drawings

The fuel injector shown in Figure 1 has a nozzle body 25 and a holding body 26 which are axially braced by means of a clamping nut, not shown. The nozzle body 25 and the holding body 26 are penetrated by a high-pressure bore 24, in which a nozzle needle 20 for releasing or closing of injection openings 27 is received in a liftable manner. The high-pressure bore 24 is connected via a feed line 28 to a high-pressure accumulator 29, via which the high-pressure bore 24 is supplied under high pressure fuel.

In the axial direction, the high-pressure bore 24 is delimited by a valve piece 1, which is inserted into the holding body 26, of a control valve for controlling the lifting movement of the nozzle needle 20. The valve piece 1 seals the high-pressure bore 24 from a low-pressure chamber 10, which is formed within a valve body 11 of the control valve. Via a bore 15 of the valve body 11, in which a valve closing element 4 of the control valve is received liftable, and a receiving space 19, in which a cooperating with an electromagnet 13 for actuating the control valve armature 12, the low-pressure chamber 10 is connected to a return line 30 ,

On the valve piece 1 of the control valve, a sealing sleeve 22 is supported, in which one end of the nozzle needle 20 is received in such a way that a control chamber 16 is formed, which is connected via an inlet throttle 18 with the high-pressure bore 24. In the closed position of the control valve therefore also prevails in the control chamber 16 high pressure, which exerts an acting on an end face 21 of the nozzle needle 20 in the closing direction compressive force. Furthermore, the nozzle needle 20 is acted upon by the spring force of a spring 23 in the closing direction. The spring 23, which is supported on the one hand on the nozzle needle 20 and on the other hand on the sealing sleeve 22, serves to restore the nozzle needle 20 and at the same time holds the sealing sleeve 22 in sealing contact with the valve piece 1 of the control valve. Via the control valve, a relief of the control chamber 16 is effected, so that the force acting on the end face 21 of the nozzle needle 20 closing pressure is reduced and the nozzle needle 20 lifts from its seat. The nozzle needle 20 releases the injection openings 27 in this way. The discharge of the control room 16 is opened by opening the

Control valve causes, so that the control chamber 16 is connected to the low-pressure chamber 10.

To open the control valve, the electromagnet 13 is energized. About the magnetic force of the electromagnet 13 of the arranged in the receiving space 19 armature 12 which is fixedly connected to the valve closing element 4 of the control valve, pulled in the direction of the electromagnet 13, so that the valve closing element 4 lifts from a formed in the valve piece 1 valve seat 2 and an outflow opening 3 releases, via which the required to relieve the control chamber 16 connection with the low-pressure chamber 10 is made. To close the control valve, the energization of the electromagnet 13 is stopped. The armature 12 and the valve closing element 4 are then placed back on the spring force of a spring 14 to its original position. In the closed position of the control valve, the control chamber 16 is filled via the inlet throttle 18 again with fuel, so that the pressure in the control chamber 16 increases again.

The outlet opening 3 is presently slit-shaped and serves at the same time as an outlet throttle 17. It lies within the valve seat 2 designed as a flat seat. For closing the outlet opening 3, the valve closure element 4 has a circular sealing surface 8, which is flat according to the valve seat 2.

In addition to the slot-shaped outflow opening 3, at least one further outflow opening 6, 6 'is provided according to the invention, which is formed within a circular area 5, which is defined by the slot-shaped outflow opening 3 and thus also comes to lie within the sealing surface 8 of the valve closing element 4. By the at least one further outflow opening 6, 6 'voltages in the valve piece 1 are counteracted, so that the load capacity of the valve piece 1 increases. Hereinafter, preferred embodiments of the further outflow openings 6, 6 'in each case in combination with a slot-shaped outflow opening 3 are shown. A first preferred embodiment is shown in FIG. It shows a usable in the fuel injector according to the figure 1 valve piece 1 of a control valve according to the invention in plan view. The further outflow opening 6 is here also slit-shaped and forms with the discharge opening 3 a cross, which comes to rest within the circular area 5, which by the length L of

Outflow opening 3 is defined. Because the length L corresponds to the diameter D of the circular surface 5. The longitudinal axes A and A 'of the two slit-shaped

Outflow openings 3, 6 are orthogonal to each other, so that the two

Outflow openings 3, 6 each cut in the middle.

A modification of the embodiment of FIG. 2 is shown in FIG. Here, a circular outflow opening 6 is arranged at the ends of the two slot-shaped outflow openings 3, 6, whose diameter d is greater than the width B of the slot-shaped outflow openings 3, 6 is selected. The circular

Outflow openings 6 cause a relief of the valve piece 1, as notch stress is counteracted.

Further modifications of the embodiments of Figures 2 and 3 are possible if - as shown in Figures 4 and 5 - a plurality of slot-shaped outflow openings 3, 6 6 'are arranged in a star shape. In this case, the star-shaped slot-shaped outflow openings 3, 6, 6 'can be connected via an intersection region or arranged at a distance from a center of the circular surface 5 so that there is no intersection. This results in a variety of possible configurations, which can not all be represented in the present case. Furthermore, the number of slit-shaped outflow openings 3, 6, 6 'can be varied and / or circular outflow openings 6 can be provided at the respective ends of the slit-shaped

Outflow openings 3, 6, 6 'are provided according to the embodiment of Figure 3.

A further, particularly preferred embodiment is shown in FIG. Here, the slot-shaped outflow opening 3 is combined with each end arranged C-shaped outflow openings 6. The C-shaped outflow openings 6 also form slots, which also extend arcuately. The arch form follows the shape of an ellipse, which is defined by the semi-axes a, b (see Figure 8). The shorter half-axis a coincides with the length L of the slot-shaped outflow opening 3, where a is less than a quarter of the length L. The ratio of the semi-axes a / b in the present case is 0.8. This has the consequence that the arcuate course of the C-shaped outflow openings 6 is offset in relation to a circle 5 delimiting the circular line inwards. This measure has a strengthening effect, because stresses occur essentially on the outside of the C-shaped

Outflow openings 6 and thus at the large radii, which are less critical with respect to stresses (see Figure 9).

A modification of the embodiment of FIG. 6 is shown in FIG. The length L of the slot-shaped outflow opening 3 here corresponds to the radius R of the circular surface 5. Respectively at the same angular distance from each other two further slot-shaped outflow openings 6 are arranged, so that the outflow openings 3, 6 give a star shape. Each of the outflow openings 3, 6 has at its end a C-shaped

Outflow opening 6 to relieve the valve piece 1. The ends of the C-shaped outflow openings 6 are compared with the circle 5 delimiting circular line inwardly offset by the amount i in order to increase the strength of the valve piece 1. Furthermore, material webs which have the dimension ii in the region between the ends of the C-shaped outflow openings 6 and the dimension iii in the radial direction remain between the slot-shaped outflow openings 3, 6. The material webs are thus dimensioned such that the valve piece 1 has sufficient strength.

FIG. 10 shows an advantageous embodiment of the valve seat 2 which can be combined with all of the embodiments of the outflow openings 3, 6, 6 'described above, although the illustration relates to an embodiment according to FIG. The valve seat 2 is formed here by webs 7, which the

Limit outflow openings 3, 6, 6 '. The webs 7 thus follow the outer contours of the outflow openings 3, 6, 6 '. The webs 7 are released over a lowered portion 9 of the valve piece 1. About the lowered area 9 of the over

Outflow openings 3, 6, 6 'exiting fuel almost pressure-free flow. For this purpose, the surface of the lowered portion 9 is larger than a cooperating with the valve seat 2 sealing surface 8 of a valve closing element 4 is selected (not shown in Figure 10). The effect of the release of the valve seat 2 will be explained in more detail with reference to FIGS 11 and 12. The valve seat 2, which is formed by webs 7, has a web surface bounding the outflow opening 3 with a web width s. This is followed by the lowered portion 9 of the valve piece 1, whereby the webs 7 are released. The fuel exiting via the discharge circumference of the outflow opening 3 (see arrows 31 in FIG. 11) can flow off largely free of pressure via the lowered region 9. The sealing surface 8 of the valve closing element 4 is therefore not acted upon by an additional pressure force acting in the opening direction when it lifts off the valve seat 2, 7 with a reduced stroke h. The closing force F required to close the control valve can thus be reduced.

In the figure 12, the applied pressure in the region of the valve seat 2 are shown. In the flow cross section of the outflow openings 3, 6, the pressure pl prevails. In the region of the web 7, the pressure of p1 drops to p3, where on average the pressure p2 prevails (p2 = (p1 + p3) / 2). Outside the lowered area 9 there is a pressure p4 which is equal to the pressure prevailing in the low-pressure space 10. The decrease in region 9 ensures that the pressure p3 approximately corresponds to the pressure p4.

The features of a control valve according to the invention which have been identified above with reference to the illustrated preferred embodiments can each be implemented individually or in different combinations. The invention is therefore not limited to the illustrated embodiments.

Claims

claims

1. Control valve for a fuel! Injector, in particular a common rail fuel injector, comprising a valve piece (1) with a formed within a seat formed as a flat seat valve seat (2) outflow opening (3) and with the valve seat (2) sealingly cooperating liftable valve closing element (4),

characterized in that the outflow opening (3) is slit-shaped and has a length (L) which is greater than a width (B), wherein the length (L) substantially a diameter (D) or a radius (R) of a Circular surface (5) corresponds within which the outflow opening (3) and at least one further with the outflow opening (3) connected and / or from the discharge opening (3) separate outflow opening (6, 6 ') are arranged.

2. Control valve according to claim 1,

characterized in that the at least one further outflow opening (6, 6 ') is slot-shaped and has a longitudinal axis (Α') which is inclined with respect to a longitudinal axis (A) of the outflow opening (3).

3. Control valve according to claim 1 or 2,

characterized in that the slot-like outflow openings (3, 6, 6 ') are arranged in a cross or star shape.

4. Control valve according to one of the preceding claims,

characterized in that the at least one further outflow opening (6) at one end of the slot-like outflow opening (3) is arranged.

5. Control valve according to one of the preceding claims,

characterized in that the at least one further outflow opening (6) is circular and has a diameter (d) which is greater than the width (B) of the slot-like outflow opening (3).

6. Control valve according to one of the preceding claims,

characterized in that the at least one further outflow opening (6) is slot-shaped and has a curved course.

7. Control valve according to claim 6,

characterized in that the arcuate course of the other

Outflow opening (6) the shape of an ellipse with two half-axes (a, b) follows, wherein the shorter half-axis (a) coincides with the length (L) of the slot-like outflow opening (3).

8. Control valve according to claim 7,

characterized in that the semiaxis (a) is less than a quarter of the length (L) of the slot-like outflow opening (3).

9. control valve according to claim 7 or 8,

characterized in that the half-axis ratio (a / b) is 0.8 to 0.9.

10. Control valve according to one of the preceding claims,

characterized in that the formed as a flat seat valve seat (2) is free and by at least one web (7) is formed, which follows an outer contour of a discharge opening (3, 6, 6 ').

11. Fuel! Njektor with a control valve according to one of the preceding claims.